VICP Registry Case Source Bundle
Canonical URL: https://vicp-registry.org/case/USCOURTS-cofc-1_19-vv-01363
Package ID: USCOURTS-cofc-1_19-vv-01363
Petitioner: Angela Hiatt
Filed: 2019-09-06
Decided: 2026-02-05
Vaccine: Tdap; HPV
Vaccination date: 2017-02-16
Condition: Guillain-Barre syndrome (GBS)
Outcome: denied
Award amount USD: 

AI-assisted case summary:
On September 6, 2019, Angela Hiatt filed a petition seeking compensation under the National Vaccine Injury Compensation Program, alleging that she developed Guillain-Barré syndrome (GBS) as a result of receiving the tetanus-diphtheria-acellular-pertussis (Tdap) and human papillomavirus (HPV) vaccines on February 16, 2017. Petitioner later narrowed her claim to focus solely on the Tdap vaccine. Ms. Hiatt, who was 45 years old at the time of vaccination, experienced no immediate adverse reaction. Eleven days post-vaccination, on February 27, 2017, she presented to an emergency department with chest and back pain, which was attributed to non-cardiac causes. She also reported upper respiratory symptoms. Over the next few days, her symptoms progressed to include weakness and numbness, and she reported a preceding gastrointestinal illness. She was hospitalized and diagnosed with GBS, characterized by absent reflexes and elevated cerebrospinal fluid protein. Ms. Hiatt required intensive care, intubation, and intravenous immunoglobulin (IVIG) treatment, followed by rehabilitation. She gradually improved but continued to experience residual neurologic sequelae. Petitioner presented expert testimony from Dr. Carlo Tornatore, a neurologist, who opined that the Tdap vaccine could trigger GBS through molecular mimicry, citing homology between tetanus toxin and nerve myelin components, and referencing government publications that advised caution with tetanus-containing vaccines in individuals with a history of GBS. Respondent presented expert testimony from Dr. Kourosh Rezania and Dr. Olajumoke Fadugba, both neurologists. Dr. Rezania conceded the GBS diagnosis but attributed its onset to a possible prior infection, doubting the Tdap vaccine's causal role due to the low risk and questioning the probative value of cited literature. Dr. Fadugba also emphasized GBS as typically post-infectious, found the evidence for a Tdap-GBS association weak, and argued that molecular mimicry was not sufficiently demonstrated for the Tdap vaccine. The Special Master, Brian H. Corcoran, denied entitlement, finding that Petitioner failed to establish by a preponderance of the evidence that the Tdap vaccine can cause GBS or did so in her case. The Special Master found Dr. Tornatore's theory to have substantive deficiencies, noting that evidence supporting the flu vaccine's link to GBS was not directly applicable to Tdap, that wild-analogs of Tdap components were not shown to be associated with GBS, that passive surveillance data and case reports were weak proof of causation, that existing epidemiologic evidence suggested no likely association, and that homology showings were speculative. The Special Master also found that government precautions regarding tetanus vaccines and GBS were inapplicable to Ms. Hiatt as she had no prior history of GBS after a Tdap vaccine. On review, the United States Court of Federal Claims, in an opinion by Judge David A. Tapp, affirmed the Special Master's decision. The Court found no legal error and that the Special Master applied the correct preponderance of the evidence standard, not requiring scientific certainty. The Court determined that the Special Master's factual findings were not arbitrary or capricious and that the petitioner's arguments regarding the interpretation of government warnings and the burden of proof were unavailing. The case was ultimately denied.

Theory of causation field:
Tdap and HPV vaccines on February 16, 2017, age 45, alleged to cause Guillain-Barre syndrome; the claim was narrowed principally to Tdap. DENIED. Petitioner relied on Dr. Carlo Tornatore and molecular mimicry/immune-mediated theory. Respondent contested diagnosis, theory, and case-specific causation. Special Master Gowen denied entitlement on October 24, 2025. Judge Carolyn N. Lerner denied petitioner's motion for review and sustained the decision on February 5, 2026; public reissue March 2, 2026 had no redactions.

Public staged source text:

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DOCUMENT 1: USCOURTS-cofc-1_19-vv-01363-0
Date issued/filed: 2025-11-19
Pages: 26
Docket text: PUBLIC DECISION (Originally filed: 10/24/2025) regarding 82 DECISION of Special Master. Signed by Chief Special Master Brian H. Corcoran. (ers) Service on parties made.
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Case 1:19-vv-01363-DAT Document 85 Filed 11/19/25 Page 1 of 26
In the United States Court of Federal Claims
OFFICE OF SPECIAL MASTERS
No. 19-1363V
* * * * * * * * * * * * * * * * * * * * * * * * *
*
ANGELA HIATT, * Chief Special Master Corcoran
*
Petitioner, * Filed: October 24, 2025
*
v. *
*
SECRETARY OF HEALTH *
AND HUMAN SERVICES, *
*
Respondent. *
*
* * * * * * * * * * * * * * * * * * * * * * * * *
Richard Gage, Law Offices of Richard Gage, Cheyenne, WY, for Petitioner.
Mary Holmes, U.S. Department of Justice, Washington, DC, Respondent.
ENTITLEMENT DECISION1
On September 6, 2019, Angela Hiatt filed a petition seeking compensation under the
National Vaccine Injury Compensation Program (the “Vaccine Program).2 Petitioner alleges that
she suffered Guillain-Barré syndrome (“GBS”) as a result of receiving the tetanus-diphtheria-
acellular-pertussis (“Tdap”) and human papillomavirus (“HPV”) vaccines on February 16, 2017.
Petition (ECF No. 1) at 1. She has since narrowed her claim to focusing solely on the Tdap vaccine.
Petitioner’s Brief, filed Feb. 25, 2025 (ECF No. 77) (“Br.”) at 6–7.
I determined that this matter could be fairly resolved via ruling on the record, and both
sides filed briefs in support of their positions. See Br.; Respondent’s Opposition, filed Mar. 26,
2025 (ECF No. 80) (“Opp.”); Petitioner’s Reply, filed Apr. 2, 2025 (ECF No. 81) (“Reply”). The
1 Under Vaccine Rule 18(b), each party has fourteen (14) days within which to request redaction “of any information
furnished by that party: (1) that is a trade secret or commercial or financial in substance and is privileged or
confidential; or (2) that includes medical files or similar files, the disclosure of which would constitute a clearly
unwarranted invasion of privacy.” Vaccine Rule 18(b). Otherwise, the whole Decision will be available to the public
in its present form. Id.
2
The Vaccine Program comprises Part 2 of the Childhood Vaccine Injury Act of 1986, Pub. L. No. 99-660, 100 Stat.
3758, codified as amended at 42 U.S.C. §§ 300aa-10 through 34 (2012) (“Vaccine Act” or “the Act”). Individual
section references hereafter will be to § 300aa of the Act (but will omit that statutory prefix).

Case 1:19-vv-01363-DAT Document 85 Filed 11/19/25 Page 2 of 26
matter is now ripe for resolution. For the reasons set forth in more detail below, I hereby deny
entitlement. Petitioner has not preponderantly established that the Tdap vaccine can cause GBS,
or did so to her.
I. Factual Background
Ms. Hiatt received both the Tdap and HPV vaccines on February 16, 2017, at the office of
her primary care provider (“PCP”). Ex. 1 at 44–46. She was 45 years old at the time. There is no
medical record evidence indicating that she experienced any unusual reaction to the vaccines in
the week immediately after.
On February 27, 2017 (now eleven days post-vaccination), Petitioner went to the
emergency department (“ED”) of McKay Dee Hospital in Ogden, Utah, with complaints of chest
and back pain that she reported had begun earlier that morning. Ex. 5 at 95. She also reported left-
sided jaw pain, which she associated with a recent sinus cold. Id. Evaluation for cardiac issues
revealed nothing of concern, and she was treated with antacids and discharged with a diagnosis of
non-cardiac chest pain. Id.
That same day Petitioner went to see her PCP for further evaluation of the pain symptoms
that had caused her to visit the ED. Ex. 1 at 42. She also reported symptoms of upper respiratory
infection with facial pressure and ear pain. Id. Her PCP assessed her with an upper respiratory
infection with non-cardiac chest and thoracic back pain, and directed her to follow up if her
symptoms did not improve. Id. at 42–43. Petitioner returned to the ED later that same day,
however, due to her concerns about worsening chest pain. Ex. 5 at 29. She was reevaluated for
cardiac issues, and also underwent a lung scan to test for pulmonary emboli, but the work-up was
negative, and she was discharged again with pain medication and antihistamines. Id.
Three days later (March 1, 2017), Ms. Hiatt went back to her PCP for evaluation of ongoing
chest pain plus weakness and hand/foot/tongue numbness. Ex. 1 at 39. She now reported that she
was experiencing nausea, vomiting, and “stomach flu” symptoms in the days before her chest pain
started (something Petitioner had not informed treaters at either of the February 27th medical
encounters, although this was deemed possibly to reflect prior gastric band surgery she had
experienced). Id. Her PCP’s impression was epigastric abdominal pain, chest pain, anemia,
weakness, and fatigue, and blood testing was ordered, along with a cardiac stress test (which
resulted in no significant findings). Id. at 40, 41.
Because of Petitioner’s ongoing symptoms, she was admitted to South Ogden Regional
Medical Center based upon a three-day history of progressive weakness and a one-week history of
back pain. Ex. 9 at 55. At this time she specifically reported a preceding gastrointestinal illness
with nausea, vomiting, and diarrhea the week prior. Id. Exam now revealed an absence of deep
tendon reflexes, weakness, and sensory deficits in her legs and arms. Id. at 59. And a thoracic spine
2

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MRI yielded normal findings, but she tested positive for elevated protein levels in her
cerebrospinal fluid. Id. at 26; 123.
Based upon her overall presentation, a consulting neurologist proposed that Petitioner had
GBS preceded by gastrointestinal flu-like illness. Ex. 9 at 26–27 (“this increase in protein by 20
over the upper range of protein for CSF as well as the cell count being normal with given history
is probably consistent with Gillain-Barre [sic] syndrome and warrant treatment for this”). She was
admitted to the intensive care unit because of respiratory distress, and within days required
intubation and ventilatory assistance. Id. at 65. While hospitalized, Petitioner received a five-day
course of IVIG, and after some gradual improvement was transferred to Northern Utah
Rehabilitation Hospital on March 15, 2017. Id. at 3–4, 118.
By April 13, 2017, Petitioner was able to walk and perform personal tasks independently,
and was discharged from rehab at that time. Ex. 6 at 40–41. She continued thereafter to experience
neurologic sequelae of her GBS, however. Ex. 4 at 8–10. She required some physical therapy that
summer, and continued to experience balance issue and limb weakness and numbness into the fall.
Ex. 1 at 21, 45; Ex. 4 at 2–4, 5–7. Other evidence of Petitioner’s medical treatment in 2018 does
not bear on causation, and I therefore do not include discussion of it herein.3
II. Expert Reports
A. Petitioner’s Expert – Dr. Carlo Tornatore
Dr. Tornatore is a neurologist, and he prepared a single written report in this case. See
Report, dated Feb. 7, 2024, filed as Ex. 36 (ECF No. 56-1) (“Tornatore Rep.”).
Dr. Tornatore graduated from Cornell University with a Bachelor of Arts and Sciences in
Neurobiology, and attended Georgetown University Medical Center, where he received a Master
of Science in Physiology. He subsequently graduated from medical school at Georgetown
University School of Medicine, completing a residency in the Department of Neurology at
Georgetown University Hospital. Tornatore Rep. at 1. Dr. Tornatore also completed a fellowship
in Molecular Virology at the National Institute of Health in Bethesda, Maryland. Id. He has
published multiple articles addressing demyelinating disorders and their pathology. Id. at 2.
Currently, Dr. Tornatore serves as a Professor and Chairman of the Department of Neurology at
Georgetown University Medical Center, Chairman and Neurologist-in-Chief of the Department of
Neurology at Medstar Georgetown University Hospital in Washington, D.C., and Medstar Health’s
3 Petitioner also filed multiple personal and witness statements that described onset and Petitioner’s state after
vaccination. See Affidavit, dated Apr. 26, 2021, filed as Ex. 14 (ECF No. 27-1); Affidavit, dated Apr. 26, 2021, filed
as Ex. 15 (ECF No. 27-2); Affidavit, dated Apr. 26, 2021, filed as Ex. 16 (ECF No. 27-3); Affidavit, dated Apr. 26,
2021, filed as Ex. 17 (ECF No. 27-4); Affidavit, dated Sep. 27, 2022, filed as Ex. 32 (ECF No. 46-1); Affidavit, dated
Nov. 1, 2022, filed as Ex. 33 (ECF No. 47-1); Physician Letter, dated Nov. 1, 2022, filed as Ex. 34 (ECF No. 47-2).
However, because this case turns on general causation, I forgo including a discussion of those documents.
3

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Regional Director Neurology. Id. at 1. Throughout his clinical career, Dr. Tornatore has cared for
several hundred patients with acute and post-acute GBS. Id. at 2.
Dr. Tornatore’s report began with a detailed review of Petitioner’s medical history,
although he stressed certain aspects of it over others. Tornatore Rep. at 2–8. For example, he
observed that her first medical encounter eleven days post-vaccination featured complaints of back
pain, which he noted could be a presenting symptom of GBS. Id. at 2–3, 20. This evolved not only
to radiating pain in the chest and jaw, but finger tingling and numbness. Id. at 3. Treaters over
time, and based upon additional exams and lab findings, embraced a GBS diagnosis, and Dr.
Tornatore found no reason to question it himself. Id. at 4–6, 8–9.
Dr. Tornatore next provided a brief explanation of GBS. He deemed it an “autoimmune
demyelinating neuropathy” impacting the peripheral nervous system, and understood to be
instigated by antigens from either a viral/bacterial infection or (in some limited cases) vaccination.
Tornatore Rep. at 9. A cross-reactive attack on nerve myelin by autoantibodies produced in
response to the stimulating foreign antigens would drive GBS. Its symptomatic features include
extremity weakness and numbness, and it could also cause facial weakness. Id.
The cross-reactivity of the autoantibodies driving GBS would occur as a result of molecular
mimicry between the presenting foreign antigens and self-tissue myelin structures. Tornatore Rep.
at 9–10; R. Hughes & D. Cornblath, Guillain-Barré Syndrome, 366 Lancet 1653, 1660 (2005),
filed as Ex. 37 (ECF No. 56-2) (“Hughes & Cornblath”). The general concept of mimicry, or shared
homology between amino acid sequences in viral/bacterial antigens and host structures, was well
accepted in science—along with the fact that this could result in antibodies produced in reaction
to a foreign antigen to mistakenly attacking self. Id. at 9. But Dr. Tornatore acknowledged that
medical science had not identified a specific cross-reactive antibody likely causal for most patients
suffering from the common form of GBS, acute inflammatory demyelinating polyneuropathy
(“AIDP”). Id. at 10–11; Hughes & Cornblath at 1659.
Nevertheless, Dr. Tornatore maintained that components of the Tdap vaccine could likely
trigger an autoimmune process leading to GBS from molecular mimicry. Tornatore Rep. at 11–12.
In support of this contention, he began with a review of government publications or notifications
that he deemed to concede this possibility. The website of the “Centers for Disease Control” (the
“CDC”), for example, notes that “certain vaccines” have been associated with GBS (although the
screenshot provided in Dr. Tornatore’s report says nothing about Tdap specifically, let alone GBS
risk due to any of its wild infectious components).4 Dr. Tornatore also referenced a document
4 Petitioner, however, only listed the URL to the CDC’s website in his report, but did not file anything as it relates to
this particular reference. See Centers for Disease Control and Prevention, Guillain-Barré Syndrome, (May 15, 2024)
https://www.cdc.gov/campylobacter/guillain-barre.html
[https://web.archive.org/web/20240515063152/https://www.cdc.gov/campylobacter/guillain-barre.html] (last visited
October 22, 2025).
4

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published in 2017 by the “Advisory Committee on Immunization Practices (the “ACIP”), which
advised treaters to take care in administering tetanus-containing vaccines to individuals who had
previously experienced GBS within six weeks of receipt of a prior dose of tetanus-containing
vaccine. Tornatore Rep. at 11–12 (citing E. Ezeanolue et al., “Best Practices Guidance of the
Advisory Committee on Immunization Practices (ACIP),” General Best Practice Guidelines for
Immunization, https://www.cdc.gov/vaccines/hcp/acip-recs/general-recs/downloads/general-
recs.pdf (2017) (last visited Oct. 22, 2025), filed as Ex. 38 (ECF No. 56-3) (“Ezeanolue”), at 54).
He also noted this precaution was repeated in the CDC “Morbidity and Mortality Weekly Report”
from 2018. J. Liang et al., “Prevention of Pertussis, Tetanus, and Diphtheria with Vaccines in the
United States: Recommendations of the Advisory Committee on Immunization Practices (ACIP),”
67 Morbidity and Mortality Weekly Report 1 (2018), filed as Ex. 39 (ECF No. 56-4).
Medical science provided a reliable reason to associate Tdap vaccine antigenic components
with GBS, Dr. Tornatore contended. Tornatore Rep. at 12–17. He pointed to existing medical and
scientific support for the idea that a specific wild bacterial infection (Campylobacter jejuni) has
been associated with GBS mediated by cross-reacting autoantibodies that (as a result of mimicry
between the antigens of the bacterial infection and nerve structures) mistakenly attacked self. Id.
at 12. But much of Dr. Tornatore’s causation theory focused not on Tdap but upon the
distinguishable influenza (“flu”) vaccine. In support, he offered some items of literature commonly
seen in Program cases, but mainly relevant to the flu vaccine or its variants. Id. at 12, 13–17.5
Nevertheless, Dr. Tornatore opined that Tdap antigens could prompt a similar cross-
reaction despite their differences from the flu vaccine components, due to molecular mimicry.
Many animal model experiments had observed that neuropathic symptoms could be induced by
flu virus or vaccine components due to amino acid sequential homology with myelin basic protein
(“MBP”)6 in live subjects.7 Tornatore Rep. at 13–16. Thus, “viruses/vaccines bearing such
5 I do not include these citations or a discussion of them—both because they are far more often than not referenced in
Program cases involving GBS, and because they are primarily relevant to the flu vaccine. See, e.g., L. Schonberger et
al., Guillain-Barré Syndrome Following Vaccination in the National Influenza Immunization Program, United States,
1976–1977, 110 Am. J. Epid. 105 (1979), filed as Ex. 42 (ECF No. 56-7) (“Schonberger”).
6 MBP is defined as “a basic protein (MW 18,000) that constitutes about 30 per cent of myelin proteins; elevated levels
of MBP occur in acute exacerbation of multiple sclerosis and acute cerebral infarction.” Myelin Basic Protein,
Dorland’s Medical Dictionary Online, https://www.dorlandsonline.com/dorland/definition?id=100535 (last visited
Oct. 22, 2025).
7 Dr. Tornatore also briefly referenced another kind of mechanism that could explain an autoimmune process prompted
by a foreign antigen—“degeneracy” of T and B cells nonspecific to the presenting antigen. Tornatore Rep. at 13; D.
Mason, A Very High Level of Crossreactivity is an Essential Feature of the T Cell Receptor, 19 Immunol. Today 395
(Sept. 1998), filed as Ex. 45 (ECF No. 56-10). But he did not provide details as to how this kind of nonspecific
activation was likely vaccine-sparked, and overall relied more heavily on the standard kind of molecular mimicry
mechanism (cross-reactivity driven by autoantibodies generated by antigenic mimics) usually featured in Program
cases.
5

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[homologous] peptides may contribute to the pathogenesis of autoimmune inflammatory CNS
activity”—and it was “unlikely that [only] a single viral peptide is responsible for the induction of
autoimmune inflammatory CNS disease.” Id. at 15.
In order to connect existing scientific support for an autoimmune mechanism for GBS in
the context of the flu vaccine to the circumstances of this case, Dr. Tornatore noted that additional
research had proposed another GBS target antigen. Tornatore Rep. at 17–18; H. Inglis et al.,
Antibody Responses to Peptides of Peripheral Nerve Myelin Proteins P0 and P2 in Patients with
Inflammatory Demyelinating Neuropathy, 78 J. Neurol. Neurosurg. Psych. 419 (2007), filed as Ex.
51 (ECF No. 57-5) (“Inglis”) (finding sample of GBS patients displayed increased antibody
reactivity to “P2” peripheral myelin protein). This P2 protein had “significant homology” with the
tetanus toxin, and Dr. Tornatore relied on his own BLAST search8 to substantiate the contention.
Tornatore Rep. at 18–19. In effect, because “epitopes from tetanus toxin bear resemblance” to a
peptide relevant to experimentally-induced forms of CNS and peripheral neuropathies, then it was
likely the same kind of mimicry could occur, and drive GBS, in the context of a Tdap vaccine’s
administration. Id. at 20.
Dr. Tornatore did, however, endeavor to offer some literature specific to the putative
association between the Tdap vaccine and GBS. For example, he cited to an article that evaluated
VAERS9 passive surveillance data. N. Souayah et al., Guillain-Barré Syndrome After Vaccination
in United States: Data from the Centers for Disease Control and Prevention/Food and Drug
Administration Vaccine Adverse Event Reporting System (1990-2005), 11 Neuromusc. Dis. 1
(2009), filed as Ex. 22 (ECF No. 20-8) (“Souayah”). Souayah noted a number of other vaccines
that might also be associated with GBS, although (a) a flu vaccine association was the most
commonly-observed, and (b) tetanus-containing vaccines came in third place in term of how often
8 According to its own website, the “Basic Local Alignment Search Tool” (BLAST) “finds regions of local similarity
between sequences. The program compares nucleotide or protein sequences to sequence databases and calculates the
statistical significance of matches. BLAST can be used to infer functional and evolutionary relationships between
sequences as well as help identify members of gene families.” https://blast.ncbi.nlm.nih.gov/Blast.cgi (last visited Oct.
22, 2025). It is common in the Program for immunology experts to utilize BLAST searches when arguing about
whether a vaccine’s protein components mimic self-structures.
9 The Vaccine Adverse Event Reporting System (“VAERS”) is a national warning system designed to detect safety
problems in U.S.-licensed vaccines. See About VAERS, VAERS, https://vaers.hhs.gov/about.html (last visited October
22, 2025). It is managed by both the CDC and the FDA. VAERS monitors and analyzes reports of vaccine related
injuries and side effects from both healthcare professionals and individuals. But it has been observed in the Program
that VAERS data is not particularly probative of causation, unless supplemented with other reliable evidence—since
a VAERS report only establishes a temporal, post-vaccination occurrence, and does not independently confirm the
reported adverse event either. See also Vig v. Sec'y of Health & Human Servs., No. 01–198V, 2013 WL 6596683, at
*17 (Fed. Cl. Spec. Mstr. Nov. 14, 2013) (“VAERS is a stocked pond, containing only reports of adverse events after
vaccinations but no data about the number of vaccines administered or the occurrence of the same adverse event in
individuals who have not been vaccinated”).
6

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post-vaccination GBS was reported. Souayah at 2 tbl. 1, 3. Souayah’s authors also acknowledged
the limitations on reliance on uncorroborated VAERS report data. Id. at 5.
Another such article is a case report—and it often surfaces in cases in which claimants
allege GBS to have been caused by the Tdap vaccine. Tornatore Rep. at 12 (citing J. Pollard & G.
Selby, Relapsing Neuropathy Due to Tetanus Toxoid: Report of a Case, 37 J. Neurol. Sci. 113
(1978), filed as Ex. 43 (ECF No. 56-8) (“Pollard & Selby”). Pollard & Selby, however, is a 47
year-old case report—and it involved an individual who experienced three documented instances
of relapse of neuropathic symptoms after receipt of a tetanus toxoid vaccine—a fact pattern
distinguishable from this Petitioner’s experience (and as noted below, there are other reasons to
question Pollard & Selby’s probative value in this case).
Dr. Tornatore also emphasized an article that observed the aforementioned relapse risk of
GBS symptoms in individuals previously diagnosed with GBS but who had received a tetanus
toxoid-containing vaccine. R. Hughes et al., Risk of Relapse of Guillain-Barré Syndrome or
Chronic Inflammatory Demyelinating Polyradiculopathy, 73 Muscle & Nerve 1230, 1231 (Sep.
1996), filed as Ex. 56 (ECF No. 57-10) (“Hughes”) (describing case series reports of 110 patients
with GBS or CIDP over 12-year period; identifying only two instances of a temporal relationship
to vaccination, but stressing (from an “overcautious” position) the risk of receiving a second
vaccine if a person experienced a symptoms relapse within 12 weeks of a prior dose). Hughes,
however (like Pollard & Selby) is far more probative of relapse risk in existing patients than to the
present circumstances).
Otherwise, Dr. Tornatore maintained that an eleven-day, post-vaccination onset was
medically acceptable, although he relied on a study specifically relevant to the flu vaccine for
support.10 Tornatore Rep. at 21–22. And he deemed it “highly improbable” that Petitioner’s
gastrointestinal symptoms explained her GBS, since a Campylobacter jejuni infection was never
confirmed, and the kind of GBS associated with such a bacterial infection was usually axonal in
nature (as opposed to AIDP, which Petitioner likely experienced). Id. at 22.
B. Respondent’s Experts
1. Kourosh Rezania, M.D. – Dr. Rezania, a neurologist, offered a single expert
report for Respondent. Report, dated Dec. 20, 2024, filed as Ex. A (ECF No. 72-1) (“Rezania
Rep.”).
Dr. Rezania received his medical degree from Tehran University School of Medicine.
Curriculum Vitae, filed as Ex. B (ECF No. 72-2) (“Rezania CV”), at 2. He then completed an
10 See Schonberger at 112 fig. 5.
7

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internship in Internal Medicine at New York Hospital, followed by his residency in Adult
Neurology at Mount Sinai Medical Center. Id. Thereafter, Dr. Rezania completed fellowships in
Neurophysiology and Neuromuscular Medicine at the University of Chicago. Id. He is currently a
professor of Neurology, as well as the Director of the Neuromuscular Fellowship Program and the
ALS Multidisciplinary Clinic at the University of Chicago Pritzker School of Medicine. Rezania
Rep. at 1. Dr. Rezania is board certified by the American Board of Psychiatry and Neurology in
Adult Neurology and Psychiatry, and Neuromuscular Medicine, in addition to Electromyography
by the American Board of Neuromuscular and Electrodiagnostic Medicine. Rezania CV at 2. He
has published over 60 peer-reviewed publications, with a primary focus on various neuromuscular
diseases, and has evaluated and treated numerous patients with GBS over the course of his clinical
career. Rezania Rep. at 1.
Dr. Rezania accepted Petitioner’s GBS diagnosis. Rezania Rep. at 3–4. He also conceded
that its onset likely occurred on February 27, 2017, as evidenced by Petitioner’s complaints of
“severe thoracic radicular pain.” Id. at 4. But Dr. Rezania gave more weight to the possibility that
it was attributable to a prior, or intercurrent, infection than did Dr. Tornatore. Her nausea and
vomiting were reported (at Petitioner’s February 27, 2017 ED visit) to have begun a few days
earlier (but after vaccination), and it was reasonable to assume a viral infection was more likely
explanatory. Id. Because Petitioner was never tested for possible “viral suspects,” however, it
could not be ascertained what might have been a credible alternative causal explanation—but
regardless, in almost half of all GBS cases only an idiopathic (and hence unidentified) cause can
be offered. Id. at 6; B. van den Berg et al., Guillain-Barre Syndrome: Pathogenesis, Diagnosis,
Treatment and Prognosis 10 Nat. Rev. Neurol 469, 469 (2014), filed as Ex. A-3 (ECF No. 73-3)
(stating that [t]wo-thirds of patients report symptoms of a recent respiratory or gastrointestinal
tract infection before the onset of GBS” … but “[i]n about half of patients with GBS, a specific
type of receding infection can be identified.”).
By contrast, Dr. Rezania doubted the Tdap vaccine could have been causal of Petitioner’s
GBS. For starters, the risk of GBS after such a vaccine was much lower than the risk associated
with the flu vaccine (and even the updated version of that vaccine posed less of a risk than the one
associated with GBS during the swine flu epidemic in the 1970s). Rezania Rep. at 4; D. Salmon et
al., Association Between Guillain-Barre Syndrome and Influenza A (H1N1) 2009 Monovalent
Inactivated Vaccines in the USA: a Meta-Analysis. 381 Lancet 1461, 1461 (2013), filed as Ex. A-
8 (ECF No. 73-8) (suggesting only a “small increased risk” of GBS associated with the influenza
A (H1N1) 2009 monovalent inactivated vaccine). At most, some case reports speculated that there
could be an association with the Tdap vaccine, but they did not constitute especially persuasive
evidence.
Dr. Rezania questioned the probative value of other items of evidence cited in Dr.
Tornatore’s Report. Ezeanolue, for example, not only settled on the less-impactful use of the word
8

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“precaution” (rather than “contraindication”), but it also suggested the absence of “strong evidence
of a significant association” between GBS and Tdap. Rezania Rep. at 4; Ezeanolue at 56. And
Souayah relied on passive surveillance data intended for use as “signal detection,” and thus was
not reliable proof of causation. Rezania Rep. at 5 (“VAERS data may be incomplete, imprecise,
incidental, or unable to be substantiated, and it should not be used independently to ascertain
vaccine-related adverse events”). In addition, Dr. Rezania challenged the probative value of
evidence offered by Dr. Tornatore specific to the flu vaccine—not only because such evidence
involved a different vaccine, but also due to the fact that the articles in question often did not
actually support causation meaningfully. Id. at 5–6.
Dr. Tornatore’s attempt to establish homologic similarity between the tetanus component
of Tdap and MBP nerve elements was also unsuccessful, in Dr. Rezania’s estimation. Rezania
Rep. at 6. Dr. Tornatore’s own personal findings (from desktop computer research) could not be
relied upon in the first place, since they did not reflect peer-reviewed and published determinations.
Id. Inglis aside, “the target antigen in the majority of AIDP (the GBS variant the petitioner had)
cases is yet unrecognized, and there is no clear evidence of molecular mimicry between specific
pathogens and components of myelin or Schwann cells in the majority of AIDP patients.” Id; N.
Shahrizaila et al., Guillain-Barre Syndrome, 397 Lancet 1214, 1218 (2021), filed as Ex. A-24 (ECF
No. 73-24) (indicating that autoantibodies against myelin proteins are not detected in individuals
with AIDP, and that anti-neurofascin antibodies are quite rare); H. Koike et al., Emerging
Infection, Vaccination, and Guillain-Barre Syndrome: A Review. 10 Neurol. Ther. 523, 523
(2021), filed as Ex. A-25 (ECF No. 73-25) (concluding that “mimicry between specific pathogens
and myelin or Schwann cell components has not been clearly demonstrated in AIDP”). Homology
alone also was not predictive of an autoimmune cross-reactive event. And Dr. Tornatore’s BLAST
research did not also include evidence suggesting what cross-reactivity would lead to—antibody
or T cells—furthering the degree to which he speculated as to the negative impact stemming from
the putative existence of homology. Rezania Rep. at 6.
2. Olajumoke Fadugba, M.D. – Dr. Fadugba is a medical and academic
immunologist, and she prepared one written report. See Report, dated Dec. 16, 2024, filed as Ex.
C (ECF No. 72-3) (“Fadugba Rep.”).
Dr. Fadugba attended the University of Delaware for her undergraduate degree, and
Vanderbilt University School of Medicine for her medical degree. Curriculum Vitae, filed as Ex.
D (ECF No. 72-4) (“Fadugba CV”), at 1. She then completed an internship and residency in
Internal Medicine at Washington University School of Medicine, followed by a fellowship in
Allergy and Immunology at Vanderbilt University School of Medicine. Id. She currently is an
Associate Professor of Clinical Medicine at the University of Pennsylvania School of Medicine,
as well as the Fellowship Program Director and Chief of the Allergy and Immunology Section at
the University of Pennsylvania. Id.; Fadugba Rep. at 1. Dr. Fadugba is board certified by the
American Board of Internal Medicine and the American Board of Allergy and Immunology.
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Fadugba CV at 1–2. She is involved in evaluating and treat vaccine responses in both a clinical
and immunologic setting, as well as vaccine reactions reported by his adult patients. Fadugba Rep.
at 1.
The initial section of Dr. Fadugba’s report featured an overview of Petitioner’s relevant
medical history. Fadugba Rep. at 2–6. She also provided a brief description of GBS, emphasizing
that it is usually a post-infectious condition (especially related to prior gastrointestinal or
respiratory symptoms). Id. at 6–9; R. Bellanti & S. Rinaldi, Guillain-Barré Syndrome: A
Comprehensive Review, 31 Eur. J. Neurol. 1, 1 (Aug. 2024), filed as Ex. C-1 (ECF No. 73-28)
(“Bellanti & Rinaldi”). GBS is associated with a number of specific infections (although not with
any of the Tdap vaccine’s component analogs). Bellanti & Rinaldi at 3. Dr. Fadugba acknowledged
that medical science hypothesized the existence of a “humoral mechanism” (meaning mediated by
antibodies) for how GBS might occur, but noted that specific “anti-myelin antibodies have yet to
be identified” (although she also allowed that certain ganglioside-specific autoantibodies were
associated with at least one variant form of GBS). Fadugba Rep. at 7, 8. Indeed, almost half of all
GBS patients did not test positive for any known autoantibodies even putatively associated with
the condition. Id.
Dr. Fadugba did not accept Dr. Tornatore’s causation theory as evidentiarily-established,
and she specifically took issue with several of his contentions. First, she denied the significance of
certain government publication statements about the risks of GBS in association with the Tdap
vaccine. Fadugba Rep. at 8–9. The ACIP precaution about administration of the Tdap vaccine to
individuals who had previously both experienced GBS and after prior Tdap vaccination itself noted
the insufficiency of evidence of causality (pro or con) with respect to the two, and that passive
surveillance data had not suggested otherwise. Fadugba Rep. at 9; Ezeanolue at 56. Thus, the
precaution against a second administration of the vaccine to individuals who previously incurred
GBS after vaccination was not itself strong evidence of causation.
Second, Dr. Fadugba deemed unpersuasive the evidence cited by Dr. Tornatore as
suggesting that molecular mimicry was a likely mechanism for how “autoimmune neurologic
conditions like GBS” occur. Fadugba Rep. at 9. Evidence specific to cross-reactivity occurring in
the wake of a Campylobacter jejuni infection, she noted, was far more robust than evidence of the
same kind of reaction after receipt of the Tdap vaccine. Id. at 9–10. Indeed, since the time of the
1970s swine flu epidemic (and resulting studies showing an association between the flu vaccine in
use at that time and GBS), subsequent studies had more often than not failed to show such a link.
See, e.g., A. Babazadeh et al., Influenza Vaccination and Guillain–Barré Syndrome: Reality or
Fear, 7 J. Trans. Intern. Med. 137, 140 (2019), filed as Ex. C-4 (ECF No. 73-31) (“Babazadeh”)
(stating that “[i]n fact [the] 1976 H1N1 influenza vaccine in New Jersey is the only proven
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association of GBS and influenza vaccination”).11 Dr. Tornatore, however, could only cite to a
number of fairly-old studies involving animal model experiments which were not only applicable
primarily to the flu vaccine, but could not be deemed strong evidence of how a human would react
to an analogous vaccine stimulus. Fadugba Rep. at 10–11. And other studies suggesting T cell
recognition of MBP could not reasonably be understood to also mean that this lead to autoimmune
disease (especially in the disparate context of a tetanus-containing vaccine). Id. at 11–12.
Dr. Fadugba similarly took issue with the argument advanced by Dr. Tornatore that (based
on his own BLAST search) homology could be demonstrated between the P2 protein (which other
studies had suggested could be an antigenic target for neuropathic autoimmune conditions) and
tetanus toxin—allowing the analogy that if the flu vaccine could react against that protein, so too
could the Tdap tetanus component. Fadugba Rep. at 12. She noted in reaction that a mere showing
of sequential homology as not enough to establish that the homologous antigen is likely to cause
an autoimmune-mediated disease process. Id. Rather, medical science understood that several
criteria needed to be satisfied. L. Peterson & R. Fujinami, Molecular Mimicry, in Autoantibodies
13–19 (2nd ed. 2007), filed as Ex. C-9 (ECF No. 73-36). But those had not been met in this case.
Dr. Tornatore’s showing of epitope similarity was too “nonspecific,” with no independent
evidence showing that the tetanus toxin was believed to have similarity with relevant host nerve
sequences, no evidence that Petitioner possessed cross-reactive antibodies that could have
prompted a pathogenic response, no independent epidemiologic evidence12 that the Tdap vaccine
likely causes GBS, and no reproducible animal model results supporting the theory either. Fadugba
Rep. at 13–14. Otherwise, Dr. Tornatore over-relied on case reports of studies interpreting passive
surveillance data—weak proof of causation. Id. at 14.
While there was overall, Dr. Fadugba opined, insufficient direct proof that the Tdap
vaccine could cause GBS, there existed sound epidemiologic evidence for the contrary position.
Fadugba Rep. at 14–15. One large-scale study involving thousands of Kaiser Permanente managed
11 Dr. Fadugba also in this context briefly questioned the persuasive value of Dr. Tornatore’s contention that immune
“degeneracy” (in which “a single T cell receptor may recognize thousands of different peptide sequences”) explained
how many vaccines could result in the same aberrant response known to occur for one, despite their differences.
Fadugba Rep. at 10. Were this true, she reasoned, one would expect to see “an unquantifiable prevalence of
autoimmune disease in the general population”—as well as any number of different environmental triggers for GBS—
yet this was not so. Id.
12 I fully recognize that the Program itself never requires claimants to offer epidemiologic evidence affirmatively
supporting their causation theory. I also note that the criteria that medical professionals or scientists might apply in
evaluating whether molecular mimicry has a persuasive explanatory basis for a given autoimmune condition is not
congruent with the Program’s causation prongs or evidence used to support them. Nevertheless—and as I have ruled
in other cases—the fact that these kind of criteria are what experts consider important in analyzing the applicability
of molecular mimicry to a given disease or illness is something a special master can reasonably consider, in evaluating
overall if it is “more likely than not” that molecular mimicry has explanatory value when affirmatively offered in a
Vaccine Act case to explain how or why a vaccine could have caused a particular injury. Cerrone v. Sec’y of Health
& Hum. Servs., No. 17-1158V, 2023 WL 3816718 (Fed. Cl. Spec. Mstr. June 1, 2023), mot. for review den’d, 168
Fed. Cl. 745 (2023), aff’d, 146 F.4th 1113 (Fed. Cir. 2025).
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care program participants identified no association between the Tdap vaccine and GBS. R. Baxter
et al., Lack of Association of Guillain-Barré Syndrome with Vaccinations, 57 Clin. Infect. Dis. 197
(July 2013), filed as Ex. C-13 (ECF No. 73-40) (“Baxter”). During the study period, only 415 cases
of GBS were confirmed (out of x>30 million person-years), and the calculated risk for developing
GBS after a tetanus vaccine between the observed six-week interval and the prior 12 months for
tetanus diphtheria combination was 1.4—which both the authors of the study and Dr. Fadugba
interpreted as not supportive of an association between the Tdap vaccine and GBS. Id. at 197;
Fadugba Rep. at 15. Baxter’s authors maximized the validity of their results by incorporating
methods that allowed them to control confounders that can render uncontrolled studies invalid,
such as only using confirmed cases of GBS, and employing a case-centered design with a
comparison group. Baxter at 197.13
Dr. Fadugba concluded with a discussion of Petitioner’s onset and its medical acceptability,
measured from the date of vaccination. Fadugba Rep. at 15–16. Dr. Tornatore offered literature
specific to the flu vaccine for this aspect of his opinion, and did not identify comparable literature
specific to tetanus-containing vaccines. Id. at 15. She admitted, however, that an 11-day onset was
otherwise “biologically plausible.” Id. Dr. Fadugba also proposed that the medical record better
supported the conclusion that a concurrent or preexisting infection explained Petitioner’s GBS,
since Petitioner’s treatment history established evidence of both “viral upper respiratory tract
symptoms” and gastrointestinal issues before or around the time of her hospitalization. Id. at 16.
III. Procedural History
The Petition was filed more than six years ago. The matter remained in “pre-assignment
review” for eight months, while Petitioner endeavored to obtain and file records relevant to the
claim. It was thereafter assigned to a different special master in the spring of 2020, and the parties
spent nearly three years attempting to settle the claim (culminating in an unsuccessful alternative
dispute resolution effort). Respondent’s Rule 4(c) Report opposing compensation was at long last
filed in April 2023 (ECF No. 53), and the parties next engaged in expert discovery through the end
of 2024. The matter was reassigned to me in the winter of 2025, and at that time I set a schedule
for ruling on the record, with briefing completed in April of this year. The claim is now ripe for
resolution.
IV. Parties’ Arguments
Petitioner
13 Dr. Fadugba also referenced a comparable study focusing on the HPV vaccine but finding no link. Fadugba Rep. at
15 (citing T. Boender et al., Risk of Guillain-Barré Syndrome after Vaccination Against Human Papillomavirus: A
Systematic Review and Meta-Analysis, 1 January 2000 to 4 April 2020, 27 Euro. Surveill. 4:2001619 (Jan. 2022), filed
as Ex. C-14 (ECF No. 73-41). However (and as noted above), because Petitioner’s causation contentions focus only
on the Tdap vaccine, I do not include analysis of the causal role, if any, of the HPV vaccine.
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Petitioner maintains that all three causation prongs established by the Federal Circuit in
Althen v. Sec'y of Health & Hum. Servs., 418 F.3d 1274, 1278 (Fed. Cir. 2005), are satisfied herein.
Br. at 8, 10, 16–17.14 First, she argues that the “can cause” prong is met. Id. at 17–22. In so
contending, Petitioner maintains that the Program has effectively “accepted” a causal association
between tetanus toxoid-containing vaccines and GBS. Br. at 22. To support this proposition, she
notes that a number of older Program cases recognized an association, relying on prior
governmental publications akin to what Dr. Tornatore invokes or independent case reports like
Pollard & Selby. Id. at 17–19. A 2011 “Institute of Medicine” publication on vaccine-associated
adverse events later downplayed the strength of evidence on the association. But it seemed to
require a level of proof approaching certainty that does not apply in Vaccine Act cases. Id. at 19–
20.
Subsequent decisions in the Program expressly recognized that the Government had likely
conceded causation over time, even if superseding publications did not expressly so state. Br. at
20–21; Mohamad v. Sec’y Health & Hum. Servs., 2022 WL 711604 (Fed. Cl. Spec. Mstr. Jan. 27,
2022), mot. for review den’d, No. 16-1075V, 2024 WL 4943421 (Fed. Cl. Nov. 12, 2024). And
some subsequent publications, like Ezeanolue, bulwarked that conclusion. Br. at 21. In addition,
more often than not Tdap-GBS cases are settled—and from that Petitioner noted “the obvious
implication is that settling so many cases seems to be an admission that Respondent accepts the
association between tetanus vaccines and GBS.” Id. at 22.
Petitioner also argues that Dr. Tornatore’s causation theory was preponderantly
established. Br. at 22–23. Dr. Tornatore observed (referencing Hughes & Cornblath) that GBS’s
pathogenesis likely implicates molecular mimicry as its mechanism, and that the homology
demonstrated by Dr. Tornatore between the tetanus toxin and the P2 protein established the
possibility of an autoimmune cross-reaction. Id. at 23. Petitioner’s contentions regarding the
second and third prongs are more succinct. Id. at 23–25. In effect, she maintains both are met
(although she only references Dr. Tornatore’s opinion with respect to the third prong in so
contending). Id. at 24.
On Reply, Petitioner insists that the tetanus vaccine can cause GBS, and in fact should be
on the Vaccine Injury Table, given the strength of evidence supporting the association. Reply at
1–2. Petitioner again points to prior decisions from Special Masters where entitlement was found
in favor of Petitioner for tetanus-GBS claims, and where Respondent settled over seventy cases
for tetanus-GBS claims. Id. (discussing Harris v. Sec’y of Health & Hum. Servs., No. 18-944V,
14 Petitioner also devoted much of her brief to the proposition that she need only demonstrate a “biologically plausible
theory,” rather than meet the preponderant, “more likely than not” standard that facially governs causation claims. Br.
at 8, 9–16. But to the extent there was previously any doubt about this question, it was disposed of by the Federal
Circuit as of this past summer. Cerrone, 146 F.4th at 1121 (a petitioner’s assertion that Althen prong one requires only
a showing of plausibility “understates the burden [a petitioner] bears under the first factor in the Althen formulation”).
I therefore do not address those aspects of Petitioner’s brief that mischaracterize her legal obligations.
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2023 WL 2583393 (Fed. Cl. Feb. 21, 2023); Mohamad, 2022 WL 711604. Further, Petitioner
argues that Respondent cannot carry his burden of establishing the existence of a causal “factor
unrelated,” since no alternatively-causal virus has been identified. Id. at 3–7.
Respondent
Respondent contends that the Petitioner has failed her requisite showing on all three Althen
prongs. First, he maintains the initial Althen “can cause” prong is not met. Opp. at 11–14. Although
Dr. Tornatore asserts that the Government has conceded a causal role of the Tdap vaccine in GBS,
the “precaution” warning in Ezeanolue did not include reliable findings of a causal relationship,
and thus constituted only a conservative warning about limited circumstances, based on a few case
report instances as well. Id. at 11–12. And it otherwise was inapplicable to Ms. Hiatt, who had not
been shown to have previously experienced post-Tdap vaccine GBS. Id. at 12.
More specifically, the theory that the Tdap vaccine could spark an autoimmune cross-
reaction via autoantibodies created due to mimicry between the vaccine’s tetanus component and
self-nerve tissues was speculative and dependent on evidence relating to other vaccines or non-
analogous infections, or studies that actually did not demonstrate pathogenic effects from
molecular mimicry’s causation of autoantibodies. Opp. at 12–13. The very concept of molecular
mimicry has widespread acceptance in the medical and scientific community—and yet no “reliable
or reproduceable evidence in the literature of tetanus vaccine causing GBS” had been offered in
this action. Id. at 13. Instead, outdated case reports (like Pollard & Selby) or studies considering
VAERS data, like Souayah, were referenced—weak support for causation. Id.
Petitioner also failed to meet the other two Althen prongs, Respondent argued. Her primary
contemporaneous treaters never accepted the Tdap vaccine as causal—while proposing a
preceding gastrointestinal illness may have been. Opp. at 14 (citing Ex. 9 at 26–27). Actual
treatment evidence, like lab work, supported this conclusion—and it was consistent with Dr.
Tornatore’s concession that most individuals who experienced GBS did so after a prior infection.
Tornatore Rep. at 11. Thus, the “did cause” prong was unmet. The timeframe prong also had not
been satisfied, since (given that prong one causation had not been demonstrated), it could not also
be shown that there was any possible medically-acceptable timeframe for onset. Opp. at 16.
V. Applicable Law
A. Petitioner’s Overall Burden in Vaccine Program Cases
To receive compensation in the Vaccine Program, a petitioner must prove either: (1) that
he suffered a “Table Injury”—i.e., an injury falling within the Vaccine Injury Table—
corresponding to one of the vaccinations in question within a statutorily prescribed period of time
or, in the alternative, (2) that his illnesses were actually caused by a vaccine (a “Non-Table
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Injury”). See Sections 13(a)(1)(A), 11(c)(1), and 14(a), as amended by 42 C.F.R. § 100.3; §
11(c)(1)(C)(ii)(I); see also Moberly ex rel. Moberly v. Sec'y of Health & Hum. Servs., 592 F.3d
1315, 1321 (Fed. Cir. 2010); Capizzano v. Sec’y of Health & Hum. Servs., 440 F.3d 1317, 1320
(Fed. Cir. 2006).15 There is no Table claim for GBS caused by a tetanus-containing vaccine.
For both Table and Non-Table claims, Vaccine Program petitioners bear a “preponderance
of the evidence” burden of proof. Section 13(1)(a). That is, a petitioner must offer evidence that
leads the “trier of fact to believe that the existence of a fact is more probable than its nonexistence
before [he] may find in favor of the party who has the burden to persuade the judge of the fact’s
existence.” Moberly, 592 F.3d at 1322 n.2; see also Snowbank Enter. v. United States, 6 Cl. Ct.
476, 486 (1984) (mere conjecture or speculation is insufficient under a preponderance standard).
Proof of medical certainty is not required. Bunting v. Sec’y of Health & Hum. Servs., 931 F.2d 867,
873 (Fed. Cir. 1991). In particular, a petitioner must demonstrate that the vaccine was “not only
[the] but-for cause of the injury but also a substantial factor in bringing about the injury.” Moberly,
592 F.3d at 1321 (quoting Shyface v. Sec'y Health & Hum. Servs., 165 F.3d 1344, 1352–53
(Fed.Cir.1999)); Pafford v. Sec’y of Health & Hum. Servs., 451 F.3d 1352, 1355 (Fed. Cir. 2006).
A petitioner may not receive a Vaccine Program award based solely on his assertions; rather, the
petition must be supported by either medical records or by the opinion of a competent physician.
Section 13(a)(1).
In attempting to establish entitlement to a Vaccine Program award of compensation for a
Non-Table claim, a petitioner must satisfy all three of the elements established by the Federal
Circuit in Althen, 418 F.3d at 1278: “(1) a medical theory causally connecting the vaccination and
the injury; (2) a logical sequence of cause and effect showing that the vaccination was the reason
for the injury; and (3) a showing of proximate temporal relationship between vaccination and
injury.”
Each of the Althen prongs requires a different showing. Under Althen prong one, petitioners
must provide a “reputable medical theory,” demonstrating that the vaccine received can cause the
type of injury alleged. Pafford, 451 F.3d at 1355–56 (citations omitted). To satisfy this prong, a
petitioner’s theory must be based on a “sound and reliable medical or scientific explanation.”
Knudsen v. Sec’y of Health & Hum. Servs., 35 F.3d 543, 548 (Fed. Cir. 1994). Such a theory must
only be “legally probable, not medically or scientifically certain.” Id. at 549.
Petitioners may satisfy the first Althen prong without resort to medical literature,
epidemiological studies, demonstration of a specific mechanism, or even a generally accepted
15 Decisions of special masters (some of which I reference in this ruling) constitute persuasive but not binding
authority. Hanlon v. Sec’y of Health & Hum. Servs., 40 Fed. Cl. 625, 630 (1998). By contrast, Federal Circuit rulings
concerning legal issues are binding on special masters. Guillory v. Sec’y of Health & Hum. Servs., 59 Fed. Cl. 121,
124 (2003), aff’d 104 F. Appx. 712 (Fed. Cir. 2004); see also Spooner v. Sec’y of Health & Hum. Servs., No. 13-159V,
2014 WL 504728, at *7 n.12 (Fed. Cl. Spec. Mstr. Jan. 16, 2014).
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medical theory. Andreu v. Sec’y of Health & Hum. Servs., 569 F.3d 1367, 1378–79 (Fed.Cir.2009)
(citing Capizzano, 440 F.3d at 1325–26). Special masters, despite their expertise, are not
empowered by statute to conclusively resolve what are essentially thorny scientific and medical
questions, and thus scientific evidence offered to establish Althen prong one is viewed “not through
the lens of the laboratorian, but instead from the vantage point of the Vaccine Act’s preponderant
evidence standard.” Id. at 1380. Accordingly, special masters must take care not to increase the
burden placed on petitioners in offering a scientific theory linking vaccine to injury. Contreras v.
Sec'y of Health & Hum. Servs, 121 Fed. Cl. 230, 245 (2015), vacated and remanded, 844 F.3d
1363 (Fed. Cir. 2017).
In discussing the evidentiary standard applicable to the first Althen prong, the Federal
Circuit has consistently rejected the contention that it can be satisfied merely by establishing the
proposed causal theory’s scientific or medical plausibility. See Cerrone v. Sec’y of Health & Hum.
Servs., 146 F.4th 1113, 1121 (Fed. Cir. 2025) (petitioner’s argument that Althen prong one requires
only a showing of plausibility “understates the burden [a petitioner] bears under the first factor in
the Althen formulation”); Kalajdzic v. Sec’y of Health & Hum. Servs., No. 2023-1321, 2024 WL
3064398, at *2 (Fed. Cir. June 20, 2024) (arguments “for a less than preponderance standard”
deemed “plainly inconsistent with our precedent” (citing Moberly, 592 F.3d at 1322)); Boatmon v.
Sec’y of Health & Hum. Servs., 941 F.3d 1351, 1359 (Fed. Cir. 2019); see also Howard v. Sec'y of
Health & Hum. Servs., 2022 WL 4869354 (Fed. Cl. Spec. Mstr. Aug. 31, 2022), mot. for review
den’d, 2023 WL 4117370, at *4 (Fed. Cl. May 18, 2023) (“[t]he standard has been preponderance
for nearly four decades”), aff’d, 2024 WL 2873301 (Fed. Cir. June 7, 2024) (unpublished). And
petitioners always have the ultimate burden of establishing their overall Vaccine Act claim with
preponderant evidence. W.C. v. Sec’y of Health & Hum. Servs., 704 F.3d 1352, 1356 (Fed. Cir.
2013) (citations omitted); Tarsell v. United States, 133 Fed. Cl. 782, 793 (2017) (noting that
Moberly “addresses the petitioner’s overall burden of proving causation-in-fact under the Vaccine
Act” by a preponderance standard).
The second Althen prong requires proof of a logical sequence of cause and effect, usually
supported by facts derived from a petitioner’s medical records. Althen, 418 F.3d at 1278; Andreu,
569 F.3d at 1375–77; Capizzano, 440 F.3d at 1326; Grant v. Sec’y of Health & Hum. Servs., 956
F.2d 1144, 1148 (Fed. Cir. 1992). In establishing that a vaccine “did cause” injury, the opinions
and views of the injured party’s treating physicians are entitled to some weight. Andreu, 569 F.3d
at 1367; Capizzano, 440 F.3d at 1326 (“medical records and medical opinion testimony are favored
in vaccine cases, as treating physicians are likely to be in the best position to determine whether a
‘logical sequence of cause and effect show[s] that the vaccination was the reason for the injury’”)
(quoting Althen, 418 F.3d at 1280). Medical records are generally viewed as particularly
trustworthy evidence, since they are created contemporaneously with the treatment of the patient.
Cucuras, v. Sec’y of Dept. of Health & Hum. Servs., 993 F.2d 1525, 1528 (Fed. Cir. 1993).
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Medical records and statements of a treating physician, however, do not per se bind the
special master to adopt the conclusions of such an individual, even if they must be considered and
carefully evaluated. Section 13(b)(1) (providing that “[a]ny such diagnosis, conclusion, judgment,
test result, report, or summary shall not be binding on the special master or court”); Snyder v. Sec’y
of Health & Hum. Servs., 88 Fed. Cl. 706, 746 n.67 (2009) (“there is nothing . . . that mandates
that the testimony of a treating physician is sacrosanct—that it must be accepted in its entirety and
cannot be rebutted”). As with expert testimony offered to establish a theory of causation, the
opinions or diagnoses of treating physicians are only as trustworthy as the reasonableness of their
suppositions or bases. The views of treating physicians should be weighed against other, contrary
evidence also present in the record—including conflicting opinions among such individuals.
Hibbard v. Sec’y of Health & Hum. Servs., 100 Fed. Cl. 742, 749 (2011) (not arbitrary or capricious
for special master to weigh competing treating physicians’ conclusions against each other), aff’d,
698 F.3d 1355 (Fed. Cir. 2012); Veryzer v. Sec’y of Dept. of Health & Hum. Servs., No. 06-522V,
2011 WL 1935813, at *17 (Fed. Cl. Spec. Mstr. Apr. 29, 2011), mot. for review den’d, 100 Fed.
Cl. 344, 356 (2011), aff’d without opinion, 475 F. Appx. 765 (Fed. Cir. 2012).
The third Althen prong requires establishing a “proximate temporal relationship” between
the vaccination and the injury alleged. Althen, 418 F.3d at 1281. That term has been equated to the
phrase “medically-acceptable temporal relationship.” Id. A petitioner must offer “preponderant
proof that the onset of symptoms occurred within a timeframe which, given the medical
understanding of the disorder’s etiology, it is medically acceptable to infer causation.” de Bazan v.
Sec’y of Health & Hum. Servs., 539 F.3d 1347, 1352 (Fed. Cir. 2008). The explanation for what is
a medically acceptable timeframe must align with the theory of how the relevant vaccine can cause
an injury (Althen prong one’s requirement). Id. at 1352; Shapiro v. Sec’y of Health & Hum. Servs.,
101 Fed. Cl. 532, 542 (2011), recons. den’d after remand, 105 Fed. Cl. 353 (2012), aff’d mem.,
503 F. Appx. 952 (Fed. Cir. 2013); Koehn v. Sec’y of Health & Hum. Servs., No. 11-355V, 2013
WL 3214877 (Fed. Cl. Spec. Mstr. May 30, 2013), mot. for rev. den’d (Fed. Cl. Dec. 3, 2013),
aff’d, 773 F.3d 1239 (Fed. Cir. 2014).
B. Legal Standards Governing Factual Determinations
The process for making determinations in Vaccine Program cases regarding factual issues
begins with consideration of the medical records. Section 11(c)(2). The special master is required
to consider “all [ ] relevant medical and scientific evidence contained in the record,” including
“any diagnosis, conclusion, medical judgment, or autopsy or coroner's report which is contained
in the record regarding the nature, causation, and aggravation of the petitioner's illness, disability,
injury, condition, or death,” as well as the “results of any diagnostic or evaluative test which are
contained in the record and the summaries and conclusions.” Section 13(b)(1)(A). The special
master is then required to weigh the evidence presented, including contemporaneous medical
records and testimony. See Burns v. Sec'y of Health & Hum. Servs., 3 F.3d 415, 417 (Fed. Cir.
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1993) (determining that it is within the special master's discretion to determine whether to afford
greater weight to contemporaneous medical records than to other evidence, such as oral testimony
surrounding the events in question that was given at a later date, provided that such determination
is evidenced by a rational determination).
As noted by the Federal Circuit, “[m]edical records, in general, warrant consideration as
trustworthy evidence.” Cucuras, 993 F.2d at 1528; Doe/70 v. Sec'y of Health & Hum. Servs., 95
Fed. Cl. 598, 608 (2010) (“[g]iven the inconsistencies between petitioner's testimony and his
contemporaneous medical records, the special master's decision to rely on petitioner's medical
records was rational and consistent with applicable law”), aff'd, Rickett v. Sec'y of Health & Hum.
Servs., 468 F. App’x 952 (Fed. Cir. 2011) (non-precedential opinion). A series of linked
propositions explains why such records deserve some weight: (i) sick people visit medical
professionals; (ii) sick people attempt to honestly report their health problems to those
professionals; and (iii) medical professionals record what they are told or observe when examining
their patients in as accurate a manner as possible, so that they are aware of enough relevant facts
to make appropriate treatment decisions. Sanchez v. Sec'y of Health & Hum. Servs., No. 11–685V,
2013 WL 1880825, at *2 (Fed. Cl. Spec. Mstr. Apr. 10, 2013); Cucuras, 993 F.2d at 1528 (“[i]t
strains reason to conclude that petitioners would fail to accurately report the onset of their
daughter's symptoms”).
Accordingly, if the medical records are clear, consistent, and complete, then they should
be afforded substantial weight. Lowrie v. Sec'y of Health & Hum. Servs., No. 03–1585V, 2005 WL
6117475, at *20 (Fed. Cl. Spec. Mstr. Dec. 12, 2005). Indeed, contemporaneous medical records
are often found to be deserving of greater evidentiary weight than oral testimony—especially
where such testimony conflicts with the record evidence. Cucuras, 993 F.2d at 1528; see also
Murphy v. Sec'y of Health & Hum. Servs., 23 Cl. Ct. 726, 733 (1991), aff'd per curiam, 968 F.2d
1226 (Fed. Cir. 1992), cert. den'd, Murphy v. Sullivan, 506 U.S. 974 (1992) (citing United States
v. United States Gypsum Co., 333 U.S. 364, 396 (1947) (“[i]t has generally been held that oral
testimony which is in conflict with contemporaneous documents is entitled to little evidentiary
weight.”)).
However, the Federal Circuit has also noted that there is no formal “presumption” that
records are accurate or superior on their face to other forms of evidence. Kirby v. Sec’y of Health
& Hum. Servs., 997 F.3d 1378, 1383 (Fed. Cir. 2021). There are certainly situations in which
compelling oral or written testimony (provided in the form of an affidavit or declaration) may be
more persuasive than written records, such as where records are deemed to be incomplete or
inaccurate. Campbell v. Sec'y of Health & Hum. Servs., 69 Fed. Cl. 775, 779 (2006) (“like any
norm based upon common sense and experience, this rule should not be treated as an absolute and
must yield where the factual predicates for its application are weak or lacking”); Lowrie, 2005 WL
6117475, at *19 (“[w]ritten records which are, themselves, inconsistent, should be accorded less
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deference than those which are internally consistent”) (quoting Murphy, 23 Cl. Ct. at 733)).
Ultimately, a determination regarding a witness's credibility is needed when determining the
weight that such testimony should be afforded. Andreu, 569 F.3d at 1379; Bradley v. Sec'y of
Health & Hum. Servs., 991 F.2d 1570, 1575 (Fed. Cir. 1993).
When witness testimony is offered to overcome the presumption of accuracy afforded to
contemporaneous medical records, such testimony must be “consistent, clear, cogent, and
compelling.” Sanchez, 2013 WL 1880825, at *3 (citing Blutstein v. Sec'y of Health & Hum. Servs.,
No. 90–2808V, 1998 WL 408611, at *5 (Fed. Cl. Spec. Mstr. June 30, 1998)). In determining the
accuracy and completeness of medical records, the Court of Federal Claims has listed four possible
explanations for inconsistencies between contemporaneously created medical records and later
testimony: (1) a person's failure to recount to the medical professional everything that happened
during the relevant time period; (2) the medical professional's failure to document everything
reported to her or him; (3) a person's faulty recollection of the events when presenting testimony;
or (4) a person's purposeful recounting of symptoms that did not exist. La Londe v. Sec'y of Health
& Hum. Servs., 110 Fed. Cl. 184, 203–04 (2013), aff'd, 746 F.3d 1334 (Fed. Cir. 2014). In making
a determination regarding whether to afford greater weight to contemporaneous medical records
or other evidence, such as testimony at hearing, there must be evidence that this decision was the
result of a rational determination. Burns, 3 F.3d at 417.
C. Analysis of Expert Testimony
Establishing a sound and reliable medical theory often requires a petitioner to present
expert testimony in support of his claim. Lampe v. Sec’y of Health & Hum. Servs., 219 F.3d 1357,
1361 (Fed. Cir. 2000). Vaccine Program expert testimony is usually evaluated according to the
factors for analyzing scientific reliability set forth in Daubert v. Merrell Dow Pharm., Inc., 509
U.S. 579, 594–96 (1993). See Cedillo v. Sec’y of Health & Hum. Servs., 617 F.3d 1328, 1339 (Fed.
Cir. 2010) (citing Terran v. Sec’y of Health & Hum. Servs., 195 F.3d 1302, 1316 (Fed. Cir. 1999).
Under Daubert, the factors for analyzing the reliability of testimony are:
(1) whether a theory or technique can be (and has been) tested; (2) whether the
theory or technique has been subjected to peer review and publication; (3) whether
there is a known or potential rate of error and whether there are standards for
controlling the error; and (4) whether the theory or technique enjoys general
acceptance within a relevant scientific community.
Terran, 195 F.3d at 1316 n.2 (citing Daubert, 509 U.S. at 592–95).
In the Vaccine Program the Daubert factors play a slightly different role than they do when
applied in other federal judicial settings, like the district courts. Typically, Daubert factors are
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employed by judges (in the performance of their evidentiary gatekeeper roles) to exclude evidence
that is unreliable or could confuse a jury. By contrast, in Vaccine Program cases these factors are
used in the weighing of the reliability of scientific evidence proffered. Davis v. Sec'y of Health &
Hum. Servs., 94 Fed. Cl. 53, 66–67 (2010) (“uniquely in this Circuit, the Daubert factors have been
employed also as an acceptable evidentiary-gauging tool with respect to persuasiveness of expert
testimony already admitted”). The flexible use of the Daubert factors to evaluate the
persuasiveness and reliability of expert testimony has routinely been upheld. See, e.g., Snyder, 88
Fed. Cl. at 742–45. In this matter (as in numerous other Vaccine Program cases), Daubert has not
been employed at the threshold, to determine what evidence should be admitted, but instead to
determine whether expert testimony offered is reliable and/or persuasive.
Respondent frequently offers one or more experts in order to rebut a petitioner’s case.
Where both sides offer expert testimony, a special master's decision may be “based on the
credibility of the experts and the relative persuasiveness of their competing theories.” Broekelschen
v. Sec'y of Health & Hum. Servs., 618 F.3d 1339, 1347 (Fed. Cir. 2010) (citing Lampe, 219 F.3d
at 1362). However, nothing requires the acceptance of an expert's conclusion “connected to
existing data only by the ipse dixit of the expert,” especially if “there is simply too great an
analytical gap between the data and the opinion proffered.” Snyder, 88 Fed. Cl. at 743 (quoting
Gen. Elec. Co. v. Joiner, 522 U.S. 146 (1997)); see also Isaac v. Sec'y of Health & Hum. Servs.,
No. 08–601V, 2012 WL 3609993, at *17 (Fed. Cl. Spec. Mstr. July 30, 2012), mot. for review
den'd, 108 Fed. Cl. 743 (2013), aff'd, 540 F. App’x 999 (Fed. Cir. 2013) (citing Cedillo, 617 F.3d
at 1339). Weighing the relative persuasiveness of competing expert testimony, based on a
particular expert's credibility, is part of the overall reliability analysis to which special masters
must subject expert testimony in Vaccine Program cases. Moberly, 592 F.3d at 1325–26
(“[a]ssessments as to the reliability of expert testimony often turn on credibility determinations”);
see also Porter v. Sec'y of Health & Hum. Servs., 663 F.3d 1242, 1250 (Fed. Cir. 2011) (“this court
has unambiguously explained that special masters are expected to consider the credibility of expert
witnesses in evaluating petitions for compensation under the Vaccine Act”).
D. Consideration of Medical Literature
Both parties filed numerous items of medical and scientific literature in this case, but not
all such items factor into the outcome of this decision. While I have reviewed all the medical
literature submitted in this case, I discuss only those articles that are most relevant to my
determination and/or are central to Petitioner’s case—just as I have not exhaustively discussed
every individual medical record filed. Moriarty v. Sec’y of Health & Hum. Servs., No. 2015–5072,
2016 WL 1358616, at *5 (Fed. Cir. Apr. 6, 2016) (“[w]e generally presume that a special master
considered the relevant record evidence even though he does not explicitly reference such evidence
in his decision”) (citation omitted); see also Paterek v. Sec’y of Health & Hum. Servs., 527 F.
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App’x 875, 884 (Fed. Cir. 2013) (“[f]inding certain information not relevant does not lead to—and
likely undermines—the conclusion that it was not considered”).
E. Determination to Resolve Case without a Hearing
I have opted to decide entitlement in this case based on written submissions and evidentiary
filings, including the expert reports filed by each side. The Vaccine Act and Rules not only
contemplate but encourage special masters to decide petitions on the papers rather than via
evidentiary hearing, where (in the exercise of their discretion) they conclude that the former means
of adjudication will properly and fairly resolve the case. Section 12(d)(2)(D); Vaccine Rule 8(d).
The choice to do so has been affirmed on appeal. See D'Toile v. Sec'y of Health & Human Servs.,
No. 15-85V, 2018 WL 1750619, at *2 (Fed. Cir. Apr. 12, 2018); see also Hooker v. Sec'y of Health
& Human Servs., No. 02-472V, 2016 WL 3456435, at *21 n.19 (Fed. Cl. Spec. Mstr. May 19,
2016) (citing numerous cases where special masters decided on the papers in lieu of hearing and
that decision was upheld). I am simply not required to hold a hearing in every matter, no matter
the preferences of the parties. See Hovey v. Sec'y of Health & Human Servs., 38 Fed. Cl. 397, 402–
03 (1997) (special master acted within his discretion in denying evidentiary hearing); Burns, 3 F.3d
at 417.
ANALYSIS
I. Overview of GBS and its Treatment in Prior Program Cases
There is no dispute in this case as to the propriety of the GBS diagnosis. See, e.g., Opp. at
11. But some discussion of the condition’s features will still be helpful in resolving causation. GBS
has been defined as an acute, monophasic peripheral neuropathy involving rapidly-progressive and
ascending weakness and paralysis, and which is thought to have an autoimmune mechanism.
Bellanti & Rinaldi at 5. It usually presents with “pain, numbness, paraesthesia, or weakness in the
limbs.” Hughes & Cornblath at 1661; Bellanti & Rinaldi at 5.
Reliable scientific evidence supports the conclusion that GBS can be vaccine-caused—
specifically by the flu vaccine (although the risk from a wild flu infection is much greater). Bellanti
& Rinaldi at 3. Consistent with this, a large body of reasoned Program decisions16 recognize an
association between the flu vaccine and GBS (as well as other related peripheral neuropathies).
Indeed, there is a Table claim for GBS due to receipt of a flu vaccine. 42 C.F.R. § 100.3.14. This
means the Government accepts that sufficiently-probative and reliable science on the topic exists
to justify conceding causation, at least for Program purposes. Haskins v. Secretary of Health &
16 Although prior decisions from different cases do not control the outcome herein, special masters may reasonably
take into account, for guidance, the logic of such reasoned determinations. In fact, it is wise to do so, given how often
similar causation theories or fact patterns arise in Vaccine Program cases.
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Hum. Servs., No. 18-1776V, WL 2020 1870279 (Fed. Cl. Spec. Mstr. Mar. 13, 2019). Even in
cases where a Table element for such a claim cannot be met (for example, when onset is too short
or too long to fit within the timeframe of 3–42 days set for the claim), any subsequent causation-
in-fact analysis performed by the special masters rarely requires the claimant to offer proof in
support of the first Althen prong, “can cause” element; instead, it is reasonably assumed to be
satisfied already. See Welch v. Sec’y of Health & Hum. Servs. No. 18-494V, 2019 WL 349360
(Fed. Cl. Spec. Mstr. July 2, 2019).
Other vaccines have also been found causal of GBS, although there is disagreement among
the special masters as to the preponderant strength of these proposed associations. See, e.g., Gross
v. Sec’y of Health & Hum. Servs., No. 17-1075, 2022 WL 9669651, at *36–37 (Fed. Cl. Spec.
Mstr. Sept. 22, 2022) (finding the pneumococcal vaccine caused GBS); but see Trollinger v. Sec’y
of Health & Hum. Servs., No. 16-473V, 2023 WL 2521912, at *30 (Fed. Cl. Spec. Mstr. Feb. 17,
2023), mot. for review den’d, 167 Fed. Cl. 127 (2023) (holding that the pneumococcal vaccine was
not shown to cause GBS); Bielak v. Sec’y of Health & Hum. Servs., No. 18-761V, 2022 WL
18058244, at *3 (Fed. Cl. Spec. Mstr. Dec. 9, 2022) (same). It thus cannot be said that the Program
has developed a consistent view as to what the science preponderantly “says” about causation of
GBS when the flu vaccine is not involved. Instead, it appears that the outcome in such cases is
mostly a function of the evidence before the special master (along with a special master’s
individual views about the applicability of causation theories to different vaccines), with no clear
trend one way or the other.
This is definitely true for claims that the Tdap vaccine can cause GBS. Several cases
decided in the past ten years (some of which I authored) found no causal association between the
two.17 See, e.g., Kaczerowski v. Sec’y of Health & Hum. Servs., No. 21-758V, 2025 WL 2798865,
at *29–38 (Fed. Cl. Spec. Mstr. Aug. 28, 2025); Dennington v. Sec'y of Health & Hum. Servs., No.
18-1303V, 2023 WL 2965239 (Fed. Cl. Spec. Mstr. Apr. 17, 2023), mot. for review den’d, 167
Fed. Cl. 640 (2023), appeal dismissed, No. 2024-1214, 2024 WL 1255318 (Fed. Cir. Mar. 25,
2024); Montgomery v. Sec’y of Health & Hum. Servs., No. 15-1037V, 2019 WL 2511352 (Fed.
Cl. Spec. Mstr. May 21, 2019); Tompkins v. Sec’y of Health & Hum. Servs., No. 10-261V, 2013
WL 3498652 (Fed. Cl. Spec. Mstr. June 21, 2013), mot. for review den’d, 117 Fed. Cl. 713 (2014);
Isaac, 2012 WL 3609993 at 19.18
17 I have also decided a few cases in which I determined that the petitioner failed to establish a causal association
between the Tdap vaccine and CIDP—a different injury from GBS, although also still a peripheral neuropathy (and
Program claimants frequently rely on GBS-specific evidence in arguing that a vaccine can cause CIDP). See, e.g.,
DeVaughn v. Sec'y of Health & Hum. Servs., No. 22-832V, 2025 WL 758128 (Fed. Cl. Spec. Mstr. Feb. 10, 2025);
Howard, 2022 WL 4869354 at *26; Sanchez v. Sec’y of Health & Hum. Servs., No. 18-1012V, 2022 WL 1013264, at
*1 (Fed. Cl. Spec. Mstr. Mar. 11, 2022).
18 I recently decided another case involving the contention that the Tdap vaccine can cause GBS, but resolution turned
on the third Althen prong, rendering that decision less valuable for guiding the present outcome. Langert v. Sec’y of
Health & Hum. Servs., No. 22-809V, 2025 WL 1892418 (Fed. Cl. Spec. Mstr. June 13, 2025).
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Prior Tdap-GBS cases have often involved causation theories comparable to what is
offered here. In my recent Kaczerowski decision, a petitioner employed Dr. Tornatore, as here.
And in that case, Dr. Tornatore relied on numerous contentions and specific items of literature that
have been offered in this case as well. See, e.g., Kaczerowski, 2025 WL 2798865, at *2–10. But I
deemed his showing not to meet the preponderant standard—even though the petitioner filed four
reports from Dr. Tornatore, allowing him ample opportunity to refine his opinion in response to
the critiques raised by Respondent’s experts.
In Isaac, a petitioner proposed molecular mimicry as the causal mechanism. Issac, 2012
WL 3609993, at *6. But the special master determined that the petitioner’s expert had over-relied
on a single case report (Pollard & Selby—also offered here) to prove causation, without adequately
substantiating the mechanism. Id. at *20–21. This determination was affirmed on appeal at the
Court of Federal Claims and Federal Circuit. In Tompkins, the special master denied entitlement
in a case alleging that a number of vaccines received at the same time (including Tdap) caused a
petitioner’s GBS, but the causal theory put forward attempted to assert that the vaccines could also
individually trigger the disease. Tompkins, 2013 WL 3498652, at *15. The petitioner’s expert,
however, relied heavily on VAERS passive surveillance data, and otherwise invoked a number of
theories (molecular mimicry, or endotoxin in tetanus-containing vaccines) that were only cursorily
substantiated. Id. at *19–23.
Admittedly (and as vociferously stressed by Petitioner), some special masters have deemed
causation demonstrated in Tdap vaccine-GBS cases. See Harris, 2023 WL 2583393; Mohamad,
2022 WL 711604, at *18. In Mohamad, a special master ruled in a petitioner’s favor in a Tdap-
GBS case, but almost wholly based on the determination that the Government had effectively
conceded the first Althen Prong. In particular, the special master observed that (a) in 2011, the
IOM had noted a precaution to receipt of the Tdap vaccine in the future if an immunized individual
had developed GBS within six weeks of a prior dose, and (b) this precaution note (along with an
acknowledgment of the possibility of encephalopathy in a seven-day timeframe) had been
maintained in subsequent ACIP reports, despite interim findings that the tetanus-GBS link was not
as well-established as previously thought. Mohamad, 2022 WL 711604, at *13–15. From this (and
also due to credibility determinations specific to the experts who had testified in that case), the
special master concluded that the first Althen prong was satisfied. Id. at *7, 15–18.
As I have noted in other cases, however, the argument that the temporal sequence of
governmental publications discussing GBS as a possible adverse event from receipt of the Tdap
vaccine, coupled with treatment advice against giving it again to a person who previously also
experienced Tdap vaccine-associated GBS, does not amount to persuasive proof that the
Government “knows” there is causal association. Kaczerowski, 2025 WL 2798865, at *34. And
efforts to broadly apply the same thinking applicable to the flu vaccine and GBS to all other
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covered vaccines are not sufficient either. Instead, a claimant seeking to prove the Tdap vaccine
caused an individual’s GBS needs to offer some overall combination of proof with some specificity
to the Tdap vaccine’s components, rather than analogizing to the flu vaccine. This showing must
be preponderantly established—not simply that it is biologically plausible a vaccine could impact
the immune system in such a way that it could lead to an autoimmune demyelinating disease, but
that it likely does so.
II. Petitioner Has not Carried Her Burden of Proof
It is understood in the Vaccine Program that because claimants must preponderantly
establish all three Althen prongs to receive damages, special masters need only evaluate those
causation elements relevant to a denial of entitlement. Dobrydnev v. Sec’y of Health & Hum.
Servs., 566 Fed. Appx. 976, 980 (Fed. Cir. 2014). Here, I find the first Althen prong has not been
satisfied (and that failure alone is grounds for denying entitlement).
First, I do not find that it has been shown that the Government has conceded a Tdap-vaccine
causal association. As noted in Kaczerowski, that kind of reasoning was actually rejected by a prior
special master in the Tompkins decision, issued in 2013—nearly 10 years before Mohamad.
Kaczerowski, 2025 WL 2798865, at *34 (referencing Tompkins, 2013 WL 3498652, at *26). It
certainly could be ascertained that Government publications have not affirmatively stated that
there is no possible Tdap vaccine-GBS relationship—and I do not conclude that either. But clearly
and over time, commentary on GBS as a possible adverse effect of receipt of a Tdap vaccine moved
away from the view that the association was well-founded to a more neutral position. While the
issue may be legitimately disputed in the context of a Vaccine Program claim, the Government
cannot be said to have conceded the point entirely.
What of the more recent publications discussing treatment precautions about the use of the
Tdap vaccine? Those precautions apply solely to circumstances not relevant to this case, since
Petitioner never had GBS before after receipt of a prior Tdap vaccine dose. Moreover (and as Dr.
Fadugba persuasively established), the precaution is itself weak proof of causation, and documents
offered to substantiate it contain equivocal statements about the strength of any purported
association. Fadugba Rep. at 9. I do not deny that this precaution provides some support for
Petitioner’s causation theory—but it is ultimately too flimsy and irrelevant to the facts of this case
to aid Petitioner all that much.
Second, Respondent’s willingness to settle petitions alleging GBS after receipt of a Tdap
vaccine is not itself reliable proof that the causation theory advanced herein has preponderant
support. I have addressed the exact same contention in other cases where I denied entitlement. See,
e.g., Howard, 2022 WL 4869354, at *22–23. No matter how many times Respondent may have
resolved cases involving the same theory or injury, the choice by a litigant to settle a case does not
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stand as evidence that the causal theory underlying such claims is correct, preponderantly-
established, or reflects reasoning the Respondent shares (and of course the decision to settle any
case is not evidence of the strength of one side’s position that can be deemed persuasive authority
by as judicial neutral). Only reasoned decisions by other special masters (which do exist—and
which admittedly in some instances are favorable to Petitioner herein) deserve any consideration
as guidance. A list of cases in which petitioners “won” is not proof of causation.
Finally, there are too many substantive deficiencies in Dr. Tornatore’s theory as
specifically crafted herein for me to find that it has been preponderantly established. As noted
above, the theory was largely consistent with what Dr. Tornatore offered in Kaczerowski—a recent
case in which I also found the Tdap vaccine-GBS association not to have been preponderantly
established, and which provides useful guidance here as well (since the theories presented in both
cases were so similar). To summarize:
• While there is evidence suggesting that flu vaccine components could cause an
autoimmune-cross reaction with MBP sufficient to spark GBS, that evidence
cannot be applied in blanket fashion to the Tdap vaccine (or other disparate
vaccines for that matter);
• The wild-analogs to the TDAP vaccine components have not been shown to be
associated with GBS (for example, a tetanus wild bacterial infection);
• Passive surveillance data or case reports are weak proof of causation, and only
demonstrate a naked temporal association with vaccination;
• Existing epidemiologic evidence better supports the conclusion that the Tdap
vaccine is not likely associated with GBS; and
• Naked showings of putative amino acid sequential homology between antigens
compared to tetanus toxin and MBP-like proteins are speculative and/or insufficient
alone to prove an autoimmune cross-reaction between Tdap vaccine and the
identified self-antigen is “more likely than not” to lead to GBS.
See Kaczerowski, 2025 WL 2798865, at *33–38.
Dr. Tornatore made no additional causation arguments that distinguish the opinion he
offered in this case from what he proposed in Kaczerowski, and identified no more recent studies
bulwarking the putative vaccine association, while relying on numerous items of literature (Pollard
& Selby; Souayah; Ezeanolue; Hughes & Cornblath) also filed in this matter. Respondent,
however, referenced herein two epidemiologic studies more directly contradicting the conclusion
that the Tdap vaccine is associated with GBS. Babazadeh at 3; Baxter at 197. As a result, I have
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been provided with no evidence in this case that would suggest I should diverge from my
determination in Kaczerowski. It has not been preponderantly demonstrated that “more likely than
not” the Tdap vaccine can cause GBS. Indeed, if anything the showing in this case (in which Dr.
Tornatore prepared a single report, not the four discussed in Kaczerowski) was even less well-
substantiated.
As a final point, I acknowledge that the special masters are not in agreement on the question
of Tdap vaccine causation of GBS, and this may lead to inconsistent outcomes. But this is
understood always to be possible in the Vaccine Program—often because the personal
medical/health circumstances of each allegedly injured party can impact the aberrant capacity of a
vaccine, as well as due to differences in the evidence offered from case to case. Special masters are
no more compelled to follow each other’s decisions than any trial judge would be in a district court.
Having now ruled in many Tdap-GBS cases, I can reasonably observe that overall the evidence
suggesting that there is a causal relationship between the two is quite thin.
CONCLUSION
A Program entitlement award is only appropriate for claims supported by preponderant
evidence. Here, Petitioner has not made such a showing. Petitioner is therefore not entitled to
compensation.
In the absence of a motion for review filed pursuant to RCFC Appendix B, the Clerk of the
Court SHALL ENTER JUDGMENT in accordance with the terms of this Decision.19
IT IS SO ORDERED.
/s/ Brian H. Corcoran
Brian H. Corcoran
Chief Special Master
19 Pursuant to Vaccine Rule 11(a), the parties may expedite entry of judgment if (jointly or separately) they file notices
renouncing their right to seek review.
26

================================================================================
DOCUMENT 2: USCOURTS-cofc-1_19-vv-01363-1
Date issued/filed: 2026-03-02
Pages: 13
Docket text: REPORTED OPINION: Opinion and Order Denying Motion for Review (ECF 91) Reissued. Signed by Judge David A. Tapp. (emc) Service on parties made.
--------------------------------------------------------------------------------
Case 1:19-vv-01363-DAT Document 93 Filed 03/02/26 Page 1 of 13
In the United States Court of Federal Claims
No. 19-1363
Filed: February 5, 2026
Reissued: March 2, 2026†
ANGELA HIATT,
Petitioner,
v.
SECRETARY OF HEALTH AND
HUMAN SERVICES,
Respondent.
Richard Gage, Richard Gage, PC, Cheyenne, Wyoming, for Petitioner.
Mary E. Holmes, Trial Attorney, Traci R. Patton, Assistant Director, Heather L. Pearlman,
Deputy Director, Jonathan D. Guynn, Acting Director, Torts Branch, Civil Division, Brett A.
Shumate, Assistant Attorney General, U.S. Department of Justice, Washington, D.C., for
Respondent.
MEMORANDUM OPINION AND ORDER
TAPP, Judge.
In this vaccine case, Petitioner, Angela Hiatt (“Ms. Hiatt”), seeks reversal of the Special
Master’s decision denying her compensation claim. Ms. Hiatt alleged that a vaccination caused
her to develop an autoimmune disorder and related neurological symptoms. The Special Master
determined that she had not proven causation by a preponderance of the evidence and denied
entitlement. Ms. Hiatt now moves for review. (Pet’r’s Mot., ECF No. 89). Ms. Hiatt’s core
argument is that the Special Master invoked the preponderance standard in name only, while
actually applying a more demanding burden. Despite these arguments, the record is devoid of
legal error or an indication that the Special Master’s fact-finding strayed into
arbitrary-and-capricious territory. Accordingly, her Motion for Review is DENIED.
† This Opinion was originally filed under seal on February 5, 2026. (ECF No. 91). The Court
provided parties the opportunity to review this opinion for any proprietary, confidential, or other
protected information and submit proposed redactions no later than February 19, 2026. Contrary
to the Court’s direction, the parties neither proposed redactions nor indicated that they were
waiving them. Thus, the sealed and public versions of this Opinion are identical, except for the
publication date and this footnote.

Case 1:19-vv-01363-DAT Document 93 Filed 03/02/26 Page 2 of 13
I. Background
Ms. Hiatt received the tetanus, diphtheria, and acellular pertussis (“Tdap”) and human
papillomavirus (“HPV”) vaccines on February 16, 2017, with no documented adverse reaction in
the days immediately following. (Petition (“Pet.”) at 1, ECF No. 1; Pet’r’s Medical Records
(“Pet’r’s Ex.”), ECF No. 6). Eleven days later, she sought medical care reporting chest and back
pain, jaw discomfort, and upper-respiratory symptoms, which her providers attributed to
non-cardiac and infectious causes rather than any post-vaccination process. (Pet’r’s Ex. 5 at 95,
ECF No. 6-5). Over the next several days, her symptoms evolved, and by March 1, she reported
new weakness and numbness, along with a history of gastrointestinal illness that she had not
mentioned during her earlier medical encounters. (Pet’r’s Ex. 1 at 39–42, ECF No. 6-1). As her
condition progressed, Ms. Hiatt was hospitalized with worsening weakness and sensory deficits,
ultimately receiving a diagnosis of Guillain–Barré syndrome (“GBS”) supported by absent
reflexes and elevated cerebrospinal fluid protein.1 (Pet’r’s Ex. 9 at 26–27, 55, ECF No. 6-9). She
required intensive care, intubation, intravenous immune globulin, and subsequent inpatient
rehabilitation, gradually improving by April 2017 but continuing to experience residual
symptoms. (Id. at 65). Ms. Hiatt initiated this action on September 6, 2019, alleging that the
Tdap and HPV vaccines caused the persistent injuries for which she seeks compensation.2 (Pet.
at 2; Pet’r’s Mot. for Review at 1–2).
The Special Master resolved Ms. Hiatt’s case on the written record with no evidentiary
hearing.3 (Entitlement Decision at 1 (“I determined that this matter could be fairly resolved via
ruling on the record, and both sides filed briefs in support of their positions.”), ECF No. 82). In
his Decision, the Special Master recounted the relevant factual and procedural background,
drawing on the medical records from the key period, medical literature, and the parties’ expert
reports. (See id. at 2–12). He ultimately found that Ms. Hiatt had not carried her burden to prove
causation. (Id. at 26).
Specifically, the Special Master determined that a petitioner alleging that the Tdap
vaccine caused GBS must present evidence tied to the components of the Tdap vaccine and must
show that the vaccine likely—not merely plausibly—caused the condition. (Entitlement Decision
at 24). He determined that the recent publications discussing Tdap-related treatment precautions
provided minimal and largely inapposite support, as those precautions concern individuals who
previously developed GBS after Tdap, which is not the case here, and the cited materials were
1 GBS is “a rare disorder in which your body’s immune system attacks your nerves. Weakness
and tingling in your hands and feet are usually the first symptoms. . . .” Gamboa-Avila v. Sec’y of
Health & Hum. Servs., 170 Fed. Cl. 441, 443 (2024) (citation omitted).
2 In her later briefing, Ms. Hiatt narrowed the claim to focus exclusively on the Tdap vaccine.
(Entitlement Decision at 1).
3 Hiatt v. Sec’y of Health & Hum. Servs., No. 19-1363V, 2025 WL 3230494, at *1 (Fed. Cl. Oct.
24, 2025) (docketed at ECF No. 82). For consistency with the parties’ briefing, the Court refers
to this decision as “Entitlement Decision” and cites to the page numbers of the docketed version.
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equivocal. (Id.). He likewise rejected the argument that the government had conceded causation,
explaining that current federal commentary on the Tdap–GBS pipeline reflects neutrality rather
than an affirmative causal acknowledgment. (Id. at 24–25). Ultimately, the Special Master found
that Ms. Hiatt’s causation theory contained too many substantive deficiencies to satisfy the
preponderance of the evidence standard. (Id. at 26).
II. Analysis
Ms. Hiatt seeks review of the Special Master’s decision and raises four principal
objections. First, she contends that the Special Master erred in his fact-finding with respect to her
Althen prong-one showing. (Pet’r’s Mot. for Review at 6–10 (citing Althen v. Secretary of Health
& Human Services, 418 F.3d 1274 (Fed. Cir. 2005)). Second, she argues that the Special Master
made findings not supported by the evidentiary record, thereby violating her due-process rights.
(Id. at 10–11). Third, she asserts that the decision improperly required her to present evidence
approaching scientific certainty. (Id. at 11–13 (citing Knudsen v. Secretary of Health & Human
Services, 35 F.3d 543, 548–49 (Fed. Cir. 1994)). Finally, she maintains that the Special Master
impermissibly heightened her burden of proof by demanding that she “preponderantly establish[]
that the Tdap vaccine can cause GBS.” (Id. at 13–19).
The Secretary responds that Ms. Hiatt’s objections lack merit. He first argues that the
Special Master applied the correct legal standard, emphasizing that the Vaccine Act and
longstanding Federal Circuit precedent make clear that Althen prong one requires proof by a
preponderance of the evidence. (Sec’y’s Resp. at 6, ECF No. 90). He further maintains that the
Special Master acted well within his discretion in finding that the government had not conceded
a causal association between the Tdap vaccine and GBS, and that this determination was neither
arbitrary nor capricious. (Id. at 11). The Secretary also disputes Ms. Hiatt’s claim that the Special
Master demanded scientific certainty, noting that the decision expressly applied the correct,
flexible framework. (Id. at 13). Finally, he contends that Ms. Hiatt’s due-process rights were not
violated. (Id. at 13–14). For the reasons stated herein, the Court denies Ms. Hiatt’s Motion and
sustains the Special Master’s decision.
A. Standard of Review
To obtain compensation under the Vaccine Program, a petitioner must establish either:
(1) that they sustained an injury listed on the Vaccine Injury Table (“Table Injury”) associated
with one of the administered vaccines and occurring within the statutorily defined time frame; or
(2) that their condition was caused-in-fact by a vaccine, constituting a “Non-Table Injury.” 42
C.F.R. § 100.3; 42 U.S.C. § 300aa-11(c)(1)(C); see Moberly ex rel. Moberly v. Sec’y of Health &
Hum. Servs., 592 F.3d 1315, 1321 (Fed. Cir. 2010); Capizzano v. Sec’y of Health & Hum. Servs.,
440 F.3d 1317, 1320 (Fed. Cir. 2006). There is no Table claim for GBS following a
tetanus-toxoid–containing vaccine.
Because Ms. Hiatt alleged an unlisted injury, her claim was considered “Non-Table,” and
she was required to prove causation. To establish causation-in-fact for a Non-Table claim, a
petitioner must satisfy the three-part test articulated in Althen v. Secretary of Health & Human
Services. 418 F.3d 1274. Under Althen, the petitioner must show by a preponderance of the
evidence: (1) a medical theory causally connecting the vaccination and the injury; (2) a logical
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sequence of cause and effect demonstrating that the vaccine caused the injury in this case; and
(3) a proximate temporal relationship between the vaccination and the onset of symptoms. Id. at
1278. The test is flexible and does not require scientific certainty, but it does require a persuasive
showing on all three prongs; failure on any defeats entitlement. Moberly, 592 F.3d at 1321;
Bunting v. Sec’y of Health & Hum. Servs., 931 F.2d 867, 873 (Fed. Cir. 1991).
For both Table and Non-Table claims, the petitioner bears the burden to establish
causation by a preponderance of the evidence—a standard that requires more than conjecture or
temporal association, but less than scientific certainty. 42 U.S.C. § 300aa-13(a)(1); Cerrone v.
Sec’y of Health & Hum. Servs., 146 F.4th 1113, 1120 (Fed. Cir. 2025); Moberly, 592 F.3d at
1321. To meet it, the petitioner must present evidence that makes their theory of causation “more
likely than not” given the entire record. See Andreu ex rel. Andreu v. Sec’y of Dep’t of Health &
Hum. Servs., 569 F.3d 1367, 1382 (Fed. Cir. 2009) (holding that “the totality of the evidence—
including the striking temporal connection between the vaccine and [petitioner’s] initial seizure,
the testimony of treating physicians, and the biologic and scientific plausibility of [petitioner’s
expert’s] theory of causation—[was] sufficient to meet the Vaccine Act’s preponderant evidence
standard”). This burden remains with the petitioner throughout the case, and it is not satisfied by
showing that a vaccine could cause the alleged injury in the abstract. See RCFC Section 13(a)(1);
W.C. v. Sec’y of Health & Hum. Servs., 704 F.3d 1352, 1356 (Fed. Cir. 2013) (citations omitted).
Rather, the petitioner must demonstrate causation as applied to their individual circumstances,
and that showing must rest on a sound and reliable medical or scientific explanation. Knudsen,
35 F.3d at 548.
On a motion for review, the Court applies the arbitrary and capricious standard to factual
findings and reviews all legal conclusions de novo. Munn v. Sec’y of Health & Hum. Servs., 970
F.2d 863, 870 n.10 (Fed. Cir. 1992). When the Court reviews mixed questions of law and fact, it
must determine whether answering it primarily involves legal or factual work. Nieves v. Sec’y of
Health & Hum. Servs., 167 Fed. Cl. 422, 428 (2023) (citing U.S. Bank Nat. Ass’n ex rel.
CWCapital Asset Mgmt. LLC v. Vill. at Lakeridge, LLC, 583 U.S. 387 (2018)). It is not this
Court’s role to reassess the evidence or substitute its own de novo factual determinations. 42
U.S.C. § 300aa-12(e); Lampe v. Sec’y of Health & Hum. Servs., 219 F.3d 1357, 1360 (Fed. Cir.
2000). Instead, the Court applies a highly deferential standard: it may set aside a Special
Master’s findings of fact only if they are arbitrary, capricious, an abuse of discretion, or
otherwise not in accordance with law. Cucuras v. Sec’y of Dep’t of Health & Hum. Servs., 26 Cl.
Ct. 537, 541 (1992), aff’d, 993 F.2d 1525 (Fed. Cir. 1993). The Court cannot “substitute its
judgment for that of the Special Master merely because it might have reached a different
conclusion.” Snyder v. Sec’y of Dep’t of Health & Hum. Servs., 88 Fed. Cl. 706, 718 (2009). A
Special Master’s determinations are upheld so long as they are “supported by evidence that is not
wholly implausible.” Hibbard v. Sec’y of Health & Hum. Servs., 698 F.3d 1355, 1363 (Fed. Cir.
2012) (quoting Cedillo v. Sec’y of Health & Hum. Servs., 617 F.3d 1328, 1338 (Fed. Cir. 2010)).
B. Objection 2: Due Process Violation
The Court begins by addressing Ms. Hiatt’s assertion that the Special Master violated her
due process rights. The argument is meritless and fails to engage with the limits of this Court’s
jurisdiction or the governing standard of review. Ms. Hiatt contends that the Special Master
made unrequested factual findings on an issue she did not present, thereby denying her due
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process. (Pet’r’s Mot. for Review at 17–18). This argument principally relates to the Special
Master’s findings in a prior case and their application here. In Kaczerowski v. Secretary of
Health & Human Services, the same Special Master considered the same expert, the same body
of medical literature, and materially similar arguments. See No. 21-758V, 2025 WL 2798865, at
*29–38 (Fed. Cl. Spec. Mstr. Aug. 28, 2025). In discussing Kaczerowski, the Special Master
noted that “the wild‑analogs to the Tdap vaccine components have not been shown to be
associated with GBS (for example, a tetanus wild bacterial infection).” (Entitlement Decision at
25 (citing 2025 WL 2798865, at *33–34)). Ms. Hiatt argues that this statement is erroneous
because she did not advance an argument concerning wild analogs. (Pet’r’s Mot. for Review at
10–11).
Ms. Hiatt misrepresents the function of that portion of the decision. The Special Master
was not making an independent factual finding about Ms. Hiatt’s case; he was summarizing the
reasoning and conclusions reached in Kaczerowski as part of his broader discussion of how
similar causation theories have been evaluated. (Entitlement Decision at 25). The summary
necessarily touched on points specific to Kaczerowski. The Special Master did not adopt those
findings, relying only on the portions relevant here. His reference to wild-analogs was merely
descriptive of the prior decision, not a factual finding about Ms. Hiatt.
Providing a summary of a related case is not arbitrary or capricious. While prior
decisions are not binding, it is neither unusual nor improper that the Special Master’s reasoning
in a prior case informed his analysis. See Davis v. Sec’y of Health & Human Servs., 94 Fed. Cl.
53, 65 (2010), aff’d, 420 F. App’x 973 (Fed. Cir. 2011) (“It is axiomatic that [S]pecial [M]asters
in vaccine cases have great leeway in building a record for decision.”). Judges and Special
Masters routinely draw on their prior evaluations of recurring experts, studies, and theories,
particularly when the evidentiary presentations substantially overlap. See Snyder, 88 Fed. Cl. at
717 (“[T]his Court has recognized the unique ability of Special Masters to adjudge cases in the
light of their own acquired specialized knowledge and expertise.”). Doing so promotes
consistency and coherence in adjudication, while still requiring each case to be decided on its
own record. Far from suggesting a due process concern, reliance on prior understanding reflects
the ordinary and legitimate effort to apply consistent reasoning to similar evidence.
Further, accepting Ms. Hiatt’s premise arguendo, allegations that a judicial officer
considered evidence she did not emphasize, misweighed the record, or articulated the governing
standards incorrectly do not, without more, amount to a constitutional violation. The Vaccine Act
provides a comprehensive and exclusive mechanism for addressing precisely these types of
objections: factual findings are reviewed for arbitrariness, and legal conclusions for correctness.
See 42 U.S.C. § 300aa-12(e). A litigant’s disagreement with how a Special Master evaluated the
record—or that the Special Master addressed an issue the petitioner did not argue—fits squarely
within that statutory review scheme. Due process does not transform routine claims of
evidentiary or legal error into constitutional injuries. See DeShaney v. Winnebago Cnty. Dep’t of
Soc. Servs., 489 U.S. 189, 200 (1989) (explaining that due process protections are triggered by
deprivations of liberty, not by alleged failures in decision-making or protection from harm). Any
genuine due‑process claim would have to be pursued through the appropriate constitutional
channels, not by reframing ordinary disagreements with the Special Master’s reasoning as a basis
for overturning the decision. Arguments of this sort are not merely unavailing; they impose
unnecessary burdens on the Court’s limited resources. When parties pursue claims that lack any
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legal foundation and fall outside the Court’s proper role, they needlessly complicate proceedings
and impede the efficient resolution of cases. Within the Vaccine Act’s tightly drawn review
structure, Ms. Hiatt’s due‑process theory does not supply a ground for disturbing the judgment.
C. Objections 1, 3, & 4: Application of Althen Prong One
Ms. Hiatt’s remaining objections relate to how the Special Master evaluated the first
prong of Althen—whether she preponderantly showed a medical theory causally connecting the
vaccination and the injury. (Pet’r’s Mot. for Review at 6–10 (Objection 1), 11–13 (Objection 3),
13–19 (Objection 4)). “Althen makes clear that a claimant’s theory of causation must be
supported by a ‘reputable medical or scientific explanation.’” Andreu, 569 F.3d at 1379 (quoting
Althen, 418 F.3d at 1278). Whether a theory of causation is “reputable” can depend on the
scientific evidence. Id. at 1380. But medical studies and data “must be viewed . . . not through
the lens of the laboratorian, but instead from the vantage point of the Vaccine Act’s preponderant
evidence standard,” which does not require “scientific certainty” or disproving “every possible
ground of causation.” Id. (citation omitted); see Broekelschen v. Sec’y of Health & Hum. Servs.,
618 F.3d 1339, 1345 (Fed. Cir. 2010); Moberly, 592 F.3d at 1325. Ms. Hiatt was therefore “not
required to present proof of causation to the level of scientific certainty,” Moberly, 592 F.3d at
1324, or to “provide conclusive evidence in the medical literature,” Andreu, 569 F.3d at 1377.
Nor was she required to support her claim with “identification and proof of specific biological
mechanisms.” Knudsen, 35 F.3d at 549. Rather, “causation can be found in vaccine cases based
on epidemiological evidence and the clinical picture.” Id. (citation omitted). It is under this
standard that the Court considers Ms. Hiatt’s remaining objections.
i. The Special Master did not err in his factual findings regarding precautions.
Ms. Hiatt’s first objection is that the Special Master’s finding that government warnings
linking tetanus vaccines to GBS do not apply to her fails both the plausibility and rational-basis
standards. (Pet’r’s Mot. for Review at 6 (referring to Entitlement Decision at 24)). She argues
this conclusion is especially flawed given a recent decision by this Court holding that similar
warnings meet those standards. (Id.). The Secretary responds that the Special Master carefully
weighed the evidentiary record, reached a supportable inference concerning the warnings at
issue, and articulated a reasoned basis for his determination. (Sec’y’s Resp. at 11–12). The Court
finds no error.
To support her theory that tetanus-toxoid–containing vaccines can cause GBS, Ms. Hiatt
relied on the expert report of Dr. Carlo Tornatore, neurologist. (Pet’r’s Ex. 36, ECF No. 56-1).
Dr. Tornatore cited two U.S. Department of Health and Human Services publications: the
Advisory Committee on Immunization Practices (“ACIP”) General Best Practice Guidelines for
Immunization and 2018 Center for Disease Control (“CDC”) Morbidity and Mortality Weekly
Report. (Pet’r’s Ex. 38, ECF No. 56-3; Pet’r’s Ex. 39, ECF No. 56-4). According to Dr.
Tornatore, both documents caution against giving a Tdap-related vaccine to anyone who
developed GBS within six weeks of a prior tetanus-toxoid dose. (Pet’r’s Ex. 36 at 12). Ms. Hiatt
characterizes this occurrence as a “challenge-rechallenge,” a recurrence pattern that can indicate
an exposure is causing an adverse reaction; she maintains that this is sufficient to show that the
Tdap vaccine may cause GBS. (Pet’r’s Mot. for Review at 8); see Capizzano, 440 F.3d 1322
(defining rechallenge). The Special Master rejected this argument. (Entitlement Decision at 23).
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Ms. Hiatt’s overarching position is that if a tetanus vaccine can cause GBS in others, it is
axiomatic that it could cause GBS as a matter of general causation, even if the recipient has not
previously had a GBS reaction. (Pet’r’s Mot. for Review at 10). She contends that the Special
Master disregarded this straightforward principle and that his contrary conclusion necessarily
lacks a rational basis. (Id.). The Special Master acknowledged that the precaution lends some
support to Ms. Hiatt’s theory. (Id. at 24). Still, he concluded that it was too slight and too
unrelated to the circumstances here to be of meaningful help. (Id. (“[T]his precaution provides
some support for Petitioner’s causation theory—but it is ultimately too flimsy and irrelevant to
the facts of this case to aid Petitioner all that much.”)). This conclusion came after analysis of the
Secretary’s immunologist expert, Dr. Olajumoke Fadugba’s, report. (Id. at 9–10). Dr. Fadugba
maintained that the precaution regarding administration of Tdap to individuals who previously
developed GBS after a tetanus-toxoid–containing dose expressly acknowledged that the evidence
of causality—either for or against—was insufficient, and that passive-surveillance data had not
suggested otherwise. (Id. at 10). Dr. Fadugba further maintained that the precaution did not
embody any reliable causal finding but instead represented a conservative advisory based on a
handful of case reports and limited to narrow circumstances. (Id. at 14).
In further support of her position that common sense indicates Tdap can cause GBS, Ms.
Hiatt relies on cases where a special master found, and was affirmed, that evidence of a
challenge-rechallenge pattern in other vaccine recipients could constitute proof of general
causation under Althen prong one. (Pet’r’s Mot. for Review at 9–10 (referring to Mohamad v.
Sec’y of Health & Hum. Servs., No. 16-1075, 2024 WL 4943421, at *7 (Fed. Cl. Nov. 12, 2024),
appeal dismissed, No. 2025-1370, 2025 WL 1341189 (Fed. Cir. May 8, 2025)). In Mohamad, the
Special Master’s conclusion that Althen prong one was met turned on findings that were
expressly tied to the evidentiary record and expert testimony presented in that case. Mohamad v.
Sec’y of Health & Hum. Servs., No. 16-1075V, 2022 WL 711604, at *17 (Fed. Cl. Jan. 27,
2022). In the Entitlement Decision for Ms. Hiatt, the Special Master distinguished Mohamad by
explaining that the holding there rested on what he understood to be the government’s effective
concession of Althen prong one, informed by the manner in which the specific precautions
interacted with the case‑specific facts and credibility findings. (Entitlement Decision at 23 (citing
Mohamad, 2022 WL 711604, at *13–15)).
The Court acknowledges that there is a divergence in how the Office of Special Masters
evaluates medical evidence concerning an alleged causal relationship between the Tdap vaccine
and GBS. See e.g., K.A. v. Sec’y of Health & Hum. Servs., 164 Fed. Cl. 98, 124 (2022)
(sustaining SM Corcoran’s decision finding no causal relationship), aff’d, No. 2023-1315, 2024
WL 2012526 (Fed. Cir. May 7, 2024); Dennington v. Sec’y of Health & Hum. Servs., No. 18-
1303V, 2023 WL 2965239 (Fed. Cl. Spec. Mstr. Apr. 17, 2023) (finding no causal relationship)
(Corcoran), mot. for review den’d, 167 Fed. Cl. 640 (2023), appeal dismissed, No. 2024-1214,
2024 WL 1255318 (Fed. Cir. Mar. 25, 2024); Montgomery v. Sec’y of Health & Hum. Servs.,
No. 15-1037V, 2019 WL 2511352 (Fed. Cl. Spec. Mstr. May 21, 2019) (finding no causal
relationship) (Moran); Rupert v. Sec’y of Health & Hum. Servs., No. 10-160V, 2014 WL 785256,
at *9 (Fed. Cl. Feb. 3, 2014) (finding no causal relationship) (Dorsey); Tompkins v. Sec’y of
Health & Hum. Servs., No. 10-261V, 2013 WL 3498652 (Fed. Cl. Spec. Mstr. June 21, 2013)
(finding no causal relationship) (Vowell), mot. for review den’d, 117 Fed. Cl. 713 (2014); but see
Winkler v. Sec’y of Health & Hum. Servs., 88 F.4th 958, 967 n.3 (Fed. Cir. 2023) (affirming SM
Dorsey’s assumption that petitioner provided a “‘proven a sound and reliable causal mechanism’
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linking . . . receipt of the Tdap vaccine to the development of GBS so as to satisfy Althen prong
one.”); Harris v. Sec’y of Health & Hum. Servs., No. 18-944V, 2023 WL 2583393, at *23 (Fed.
Cl. Feb. 21, 2023) (finding a causal relationship) (Horner); Mohamad, 2022 WL 711604, at *17
(Fed. Cl. Jan. 27, 2022) (finding a causal relationship) (Moran), review denied, decision aff’d,
No. 16-1075, 2024 WL 4943421 (Fed. Cl. Nov. 12, 2024); Swaiss v. Sec’y of Health & Hum.
Servs., No. 15-286V, 2019 WL 6520791, at *27 (Fed. Cl. Nov. 4, 2019) (finding causal
relationship) (Gowen). Some decisions have found that petitioners met their burden under Althen
based on the particular expert testimony and record presented, while others, often on materially
different records, have concluded that the evidence was insufficient to establish causation.
(Entitlement Decision at 18). The Special Master acknowledged this rift in his Entitlement
Decision. (Id. at 22).
The existence of differing outcomes does not signal a recognized causal association
between Tdap and GBS, nor does it create a binding precedent that would compel a Special
Master to reach a particular conclusion in any given case. See Boatmon v. Sec’y of Health &
Hum. Servs., 941 F.3d 1351, 1358 (Fed. Cir. 2019) (“[a] Special Master is not bound to follow
the opinions of other Special Masters.”). This variation reflects the fact-specific nature of
Vaccine Act adjudication, not a settled legal or scientific consensus in either direction. Special
Masters are charged with weighing the evidence before them, assessing the credibility of
competing experts, and applying the Althen framework to the unique factual record of each
petition. Snyder, 88 Fed. Cl. at 717. That some Special Masters have found causation on certain
records while others have not underscores that these determinations turn on the strength and
coherence of the evidence presented, not on any uniform view within the Office of Special
Masters about Tdap and GBS. Knudsen, 35 F.3d at 548 (“[c]ausation in fact under the Vaccine
Act is . . . based on the circumstances of the particular case.”); (see Entitlement Decision at 22).
Ms. Hiatt also notes in her Motion for Review that Mohamad was later sustained by
another judge of this Court. (Pet’r’s Mot. for Review at 9–10 (citing Mohamad, 2024 WL
4943421, at *9 (Hadji, J.))). Ms. Hiatt emphasizes that this affirmance went unmentioned in the
Entitlement Decision, a silence she believes understates the significance of the case.4 (Id. at 10).
This Court affirmed that evidence of the “rechallenge” paradigm in other vaccine recipients can
constitute proof of general causation under Althen prong one. Mohamad, 2024 WL 4943421, at
*9 n.10. That ruling merely illustrates why the Special Master’s analysis was not arbitrary or
capricious—it does not establish that the challenge-rechallenge paradigm is itself a legally
required or sufficient showing under Althen. Stated differently, the fact that such evidence can
satisfy an evidentiary burden does not mean that it invariably does. The arbitrary-and-capricious
standard lives a double life; it necessarily allows for divergent but reasonable outcomes. The
question is not whether another decision might also have been reasonable, but whether the one
reached is within the bounds of rational decision-making. Provided the Special Master has
4 As a general rule, the Special Master was not required to discuss that case as it constitutes non-
binding precedent. Boatmon v. Sec’y of Health & Hum. Servs., 941 F.3d 1351, 1358 (Fed. Cir.
2019); see also Hanlon v. Sec’y of Health & Human Servs., 40 Fed. Cl. 625, 630 (1998),
(“Special masters are neither bound by their own decisions nor by cases from the Court of
Federal Claims[.]”) aff’d, 191 F.3d 1344 (Fed. Cir. 1999).
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considered the evidence and articulated a rational basis for his conclusions, the mere possibility
that another adjudicator might have decided the matter differently does not render the decision
unlawful. See Hines ex rel. Sevier v. Sec’y of Dep’t of Health & Hum. Servs., 940 F.2d 1518,
1528 (Fed. Cir. 1991) (“If the [S]pecial [M]aster has considered the relevant evidence of record,
drawn plausible inferences and articulated a rational basis for the decision, reversible error will
be extremely difficult to demonstrate.”). Although Mohamad was sustained, that outcome does
not determine whether Ms. Hiatt has met her burden, and its affirmance does not justify remand
or reversal.
That the Department of Health and Human Services issued precautions that apply only to
individuals who previously developed GBS after a tetanus-toxoid dose was a central aspect of
the Special Master’s reasoning. (See Entitlement Decision at 24). The Secretary argued that,
despite the government publications, the warnings from the ACIP and CDC could not advance
Ms. Hiatt’s Althen prong-one theory because she had no history of GBS following an earlier
tetanus-containing vaccination. (Sec’y’s Resp. at 12). Accepting that argument, the Special
Master captured the point succinctly: the precaution “was inapplicable to Ms. Hiatt, who had not
been shown to have previously experienced post-Tdap vaccine GBS.” (Entitlement Decision at
14). In examining cases where a causal relationship was found, the Special Master found those
decisions distinguishable because they involved either effective concessions on Althen prong one
or case-specific credibility assessments that are absent here. (Id. at 24). Although the precautions
reasonably lend support to Ms. Hiatt’s position that Tdap may, in some circumstances, be
associated with GBS, a precaution remains just that—a conservative measure rather than an
admission of causation. The Special Master’s conclusion that these warnings do not establish that
Tdap can cause GBS, particularly when evaluated against the record, reflects a reasoned
assessment of their limited probative value and therefore cannot be deemed arbitrary.
ii. The Special Master did not require proof of scientific certainty.
The Court is also not persuaded by Ms. Hiatt’s claim that the Special Master required
proof of scientific certainty in contravention of legal precedent. Ms. Hiatt argues that the Special
Master’s findings demonstrate that he applied an improperly heightened burden of proof. (Pet’r’s
Mot. for Review at 10–11 (referring to statements that “epitope similarity was too nonspecific,”
that there was “no evidence that Petitioner possessed cross‑reactive antibodies,” and that there
was no “epidemiologic evidence”) (citing Entitlement Decision at 6, 11))). According to Ms.
Hiatt, these expectations collectively amount to a requirement of near‑definitive mechanistic
proof, far beyond what the preponderance of the evidence standard requires. (Id. at 11).
The Secretary contends, and the Court agrees, that although Ms. Hiatt frames her
objection as a legal challenge, it amounts to a disagreement with the Special Master’s weighing
of the expert evidence and a misunderstanding of his findings. (Sec’y’s Resp. at 13). The
passages on which Ms. Hiatt relies are not findings or legal conclusions at all; they are
summaries of the expert reports. Section II of the Decision serves only to recount the parties’
submissions, not to resolve them. (Entitlement Decision at 3–12). When a decision simply
recounts the contents of an expert report without adopting or analyzing its conclusions, that
recitation functions as dicta rather than a finding of fact. See Obiter Dictum, BLACK’S LAW
DICTIONARY (12th ed. 2024) (“A judicial comment made while delivering a judicial opinion, but
one that is unnecessary to the decision in the case and therefore not precedential (although it may
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be considered persuasive).”); Co-Steel Raritan, Inc. v. Int’l Trade Comm’n., 357 F.3d 1294, 1307
(Fed. Cir. 2004) (“Because statements made in dicta do not implicate the substantive holding of
the case, they cannot be considered binding authority.”) (internal quotations omitted). Treating
those summaries as if they reflected the Special Master’s own determinations misapprehends the
structure of the Decision and obscures the actual findings that appear later in the analysis.
Because Ms. Hiatt’s argument is premised on a misreading of the Special Master’s findings, it is
unavailing.
To the extent Ms. Hiatt invites the Court to reweigh the evidence, that invitation must be
declined. See Lampe, 219 F.3d at 1360. While the Special Master “must review record evidence
to assess the preponderance standard,” he is “at liberty to determine the weight of each piece of
evidence.” Faulkenberry v. Sec’y of Health and Human Servs., 176 Fed. Cl. 700, 707 (2025)
(citations omitted). That said, a causation theory must only be “legally probable, not medically or
scientifically certain.” Knudsen, 35 F.3d at 549. A review of the Entitlement Decision confirms
that the Special Master did not demand scientific certainty or impose an unduly rigorous burden
of proof. Instead, he evaluated the evidence Ms. Hiatt submitted and found it insufficient under
the preponderance standard. His observations regarding epitope similarity, cross-reactive
antibodies, and epidemiologic data, (Entitlement Decision at 6, 11), reflected an assessment of
the strength of Ms. Hiatt’s theory, not the imposition of inflexible legal prerequisites. Based on
the record, the Special Master reasonably determined that Ms. Hiatt had not met her burden
under Althen without requiring definitive scientific proof of causation.
iii. The Special Master did not heighten the burden of proof.
Finally, Ms. Hiatt contends that the Special Master improperly elevated the standard
under Althen prong one by requiring not merely a “reputable” medical theory, but affirmative
proof that the vaccine can cause the alleged injury. (Pet’r’s Mot. for Review at 13). Ms. Hiatt
states that this approach effectively disregards the long-recognized principle that a petitioner may
satisfy prong one by presenting a biologically plausible theory, proven by a preponderance of the
evidence. (Id. at 13–14). She argues that the standard applied exceeds what is legally required
and imposes a burden unattainable under current scientific understanding. (Id. at 14). The
Secretary reasons that the Special Master applied the correct preponderance standard. (Sec’y’s
Resp. at 6). The Court finds that while a biologically plausible theory is a necessary component
of a petitioner’s case, it must be substantiated by reliable evidence that, taken as a whole,
establishes causation by a preponderance of the evidence; the Special Master did not misapply
this standard.
Ms. Hiatt appears to treat the biologically plausible medical theory and the
preponderance of the evidence standard as distinct and independent requirements. They are not.
In vaccine injury cases, the preponderance of the evidence standard and the requirement of a
biologically plausible medical theory under Althen prong one work together to define both the
nature and degree of proof a petitioner must provide to establish causation. See 42 U.S.C. §
300aa13(a)(1); Althen, 418 F.3d at 1280. The biologically plausible theory sets the framework: it
must offer a scientifically credible explanation for how the vaccine could cause the alleged
injury. Knudsen, 35 F.3d at 549. This theory need not be universally accepted or proven to a
scientific certainty; rather, it must be grounded in reliable medical or scientific principles and
rise above mere speculation. Id. Once such a theory is articulated, the petitioner must then prove
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it by a preponderance of the evidence—that is, show it is more likely than not that the vaccine
caused the injury. White v. Sec’y of Health & Hum. Servs., ___ F. 4th. ___, 2025 WL 3703259,
at *4 (Fed. Cir. Aug. 27, 2025) (citing Lobo v. Dep’t of Just., 139 F.4th 1311, 1317 (Fed. Cir.
2025) (noting that “‘medical certainty’ . . . is more demanding than the preponderance standard
of more likely than not”)). This evidentiary standard allows for flexibility, recognizing that direct
proof is often unavailable in complex medical cases. Althen, 418 F.3d at 1279. Circumstantial
evidence, expert opinion, and logical inference may suffice. Id. at 1280. Together, these
standards ensure that petitioners are not held to an unattainable scientific threshold, while still
requiring a rational and persuasive showing of causation based on the specific facts of the case.
Put simply, plausibility must be proven by a preponderance of the evidence.
Ms. Hiatt correctly observes that Althen prong one is satisfied by presenting a
biologically plausible medical theory, so long as that theory is supported by reliable evidence,
which may include circumstantial proof. (Pet’r’s Mot. for Review at 14). She argues that the
Special Master departed from this standard by effectively requiring her to demonstrate that the
Tdap vaccine actually “can cause” GBS, a level of proof she describes as scientifically
unattainable. (Id.). Notably, however, Ms. Hiatt herself characterizes Althen prong one in nearly
identical terms earlier in her Motion for Review, stating that prong one “asks a Petitioner to
show that a vaccine can cause, (general causation), an injury.” (Id. at 10 (emphasis in original)).
In the end, it is difficult to discern any meaningful distinction between the standard Ms. Hiatt
advocates and the one she criticizes the Special Master for applying.
In addressing the evidentiary standard under the first Althen prong, the Federal Circuit
has repeatedly made clear that it is not enough for a petitioner to present a causation theory that
is merely scientifically or medically plausible. See Cerrone, 146 F.4th at 1121 (rejecting the
notion that plausibility alone satisfies prong one); Kalajdzic v. Sec’y of Health & Hum. Servs.,
No. 2023-1321, 2024 WL 3064398, at *2 (Fed. Cir. June 20, 2024) (reaffirming that arguments
advocating “a less than preponderance standard” are “plainly inconsistent with [Circuit]
precedent” (citing Moberly, 592 F.3d at 1322)); Boatmon, 941 F.3d at 1359 (emphasizing that
plausibility must be supported by reliable evidence). While a petitioner must present a
biologically plausible medical theory explaining how the vaccine could cause the alleged injury,
that theory must also be supported by evidence sufficient to meet the preponderance of the
evidence standard. Knudsen, 35 F.3d at 548–49 (the standard of proof for causation under the
Vaccine Act is “probable” and “preponderance”).
Despite Ms. Hiatt’s assertions, a theory alone is insufficient to satisfy the burden under
Althen prong one. (Pet’r’s Mot. for Review at 15–16). The theory is the starting point, as it
defines what the petitioner is trying to prove. But the petitioner must also provide some support
that the theory is plausible in the context of the case. Assessment of that theory “is made through
the standards of the Vaccine Act’s preponderance evidence test, not through the standards of
rigorous medical research[.]” Doles v. Sec’y of Health & Hum. Servs., No. 2023-2404, 2025 WL
1177875, at *3 (Fed. Cir. Apr. 23, 2025) (citing Andreu, 569 F.3d at 1380). The Special Master
then evaluates the quality, reliability, and coherence of that evidence. Burns v. Sec’y of Health &
Hum. Servs., 3 F.3d 415, 417 (Fed. Cir. 1993) (noting that a special master has discretion to
determine the relative weight of the evidence, including medical records). Thus, a theory without
some level of satisfactory evidentiary support is insufficient. The petitioner must bridge the gap
between theory and proof with persuasive evidence tailored to the facts of the case. Exum v.
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Sec’y of Health & Hum. Servs., 178 Fed. Cl. 627, 650 (2025) (affirming Special Master’s
requirement that the petitioner must “knit[ ] together . . . an overall theory that does not amount
to speculation or unreasonable extrapolation.”). As the Federal Circuit recently affirmed, “the
evidence a claimant offers must, in totality, always accomplish one thing in the end:
preponderantly establish that the vaccine(s) at issue more likely than not can cause the relevant
disease.” Cerrone, 146 F.4th at 112 (emphasis removed). In Ms. Hiatt’s case, the Special Master
correctly identified and applied the governing standard. It appears that Ms. Hiatt’s objections on
this point relate to the weight assigned to the evidence she presented, rather than the legal
framework employed by the Special Master. The Court has already found that his findings were
rational.
As part of her argument, Ms. Hiatt contends that the Federal Circuit itself has misapplied
the Althen prong one standard in recent years. (Pet’r’s Mot. for Review at 18 (referring to
Boatmon, 941 F.3d 1351 and Cerrone, 146 F.4th 1113 as “aberrant” to Althen)). She asserts that
these decisions have impermissibly elevated a petitioner’s burden by requiring definitive proof of
causation, rather than a reliable and biologically plausible theory supported by a preponderance
of the evidence. (Id.). In her view, this trend reflects a departure from the flexible evidentiary
framework that Althen was intended to preserve. (Id.). Whether Ms. Hiatt believes the Federal
Circuit has veered off course from Althen is ultimately a matter for her to raise with that court.
This Court is bound to follow the route the Circuit charts. If a course correction is warranted, it is
the Circuit—not this Court—that holds the map and the wheel.
Viewed through the deferential lens required by the Vaccine Act, Ms. Hiatt’s objections
do not warrant disturbing the Special Master’s decision. Her challenges to his fact-finding
amount to disagreements with how the evidence was weighed, not demonstrations that the
findings were improper. The record reflects a careful and transparent evaluation of the medical
records, expert reports, and competing theories. Nothing in Ms. Hiatt’s submissions identifies a
factual determination that approaches arbitrariness or caprice or a misapplication of the
governing legal standards. The decision does not suggest that the Special Master required
scientific certainty or otherwise heightened Ms. Hiatt’s burden; he applied the Althen framework
and the preponderance standard as precedent requires. Because the Court’s role is limited to
ensuring that the Special Master acted rationally and within the bounds of law, the decision must
be sustained.5
5 Ms. Hiatt requests that the Court remand this matter with instructions that it be reassigned to
Special Master Young. (Pet’r’s Mot. for Review at 20). Even assuming Ms. Hiatt had prevailed
on the merits, she has not established good cause to justify reassignment. The record lacks any
indication of bias, misconduct, or other exceptional circumstances that would warrant removal of
the Special Master. Moreover, the Court is guided by the well-established principle that litigants
do not have the right to choose their adjudicator.
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III. Conclusion
Framed against the proper standard of review, Ms. Hiatt’s objections fall short, and the
record provides no basis to disturb the Special Master’s well-supported decision. Because she
has identified no legal error and no improper factual determination that meets the threshold for
reversal, the Court DENIES her Motion for Review, (ECF No. 89), and SUSTAINS the Special
Master’s decision, (ECF No. 82). The Clerk is directed to enter judgment accordingly.
The Court has filed this ruling under seal. The parties shall confer to determine proposed
redactions to which the parties agree. Per Vaccine Rule 18(b), fourteen (14) days from the date
of this decision, the parties shall file a Joint Status Report indicating their agreement with the
proposed redactions, attaching a copy of those pages of the Court’s ruling containing proposed
redactions, with all proposed redactions clearly indicated.
IT IS SO ORDERED.
s/ David A. Tapp
DAVID A. TAPP, Judge
13

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DOCUMENT 3: USCOURTS-cofc-1_19-vv-01363-2
Date issued/filed: 2026-03-02
Pages: 13
Docket text: **RE-DOCKETED 93 FOR PUBLICATION**JUDGE VACCINE REPORTED OPINION (PUBLIC VERSION) re: 91 Judge Vaccine Order/Opinion Signed by Judge David A. Tapp. (tjk) Service on parties made. Modified on 3/18/2026 to add re-docketed language. (fm).
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Case 1:19-vv-01363-DAT Document 95 Filed 03/02/26 Page 1 of 13
In the United States Court of Federal Claims
No. 19-1363
Filed: February 5, 2026
Reissued: March 2, 2026†
ANGELA HIATT,
Petitioner,
v.
SECRETARY OF HEALTH AND
HUMAN SERVICES,
Respondent.
Richard Gage, Richard Gage, PC, Cheyenne, Wyoming, for Petitioner.
Mary E. Holmes, Trial Attorney, Traci R. Patton, Assistant Director, Heather L. Pearlman,
Deputy Director, Jonathan D. Guynn, Acting Director, Torts Branch, Civil Division, Brett A.
Shumate, Assistant Attorney General, U.S. Department of Justice, Washington, D.C., for
Respondent.
MEMORANDUM OPINION AND ORDER
TAPP, Judge.
In this vaccine case, Petitioner, Angela Hiatt (“Ms. Hiatt”), seeks reversal of the Special
Master’s decision denying her compensation claim. Ms. Hiatt alleged that a vaccination caused
her to develop an autoimmune disorder and related neurological symptoms. The Special Master
determined that she had not proven causation by a preponderance of the evidence and denied
entitlement. Ms. Hiatt now moves for review. (Pet’r’s Mot., ECF No. 89). Ms. Hiatt’s core
argument is that the Special Master invoked the preponderance standard in name only, while
actually applying a more demanding burden. Despite these arguments, the record is devoid of
legal error or an indication that the Special Master’s fact-finding strayed into
arbitrary-and-capricious territory. Accordingly, her Motion for Review is DENIED.
† This Opinion was originally filed under seal on February 5, 2026. (ECF No. 91). The Court
provided parties the opportunity to review this opinion for any proprietary, confidential, or other
protected information and submit proposed redactions no later than February 19, 2026. Contrary
to the Court’s direction, the parties neither proposed redactions nor indicated that they were
waiving them. Thus, the sealed and public versions of this Opinion are identical, except for the
publication date and this footnote.

Case 1:19-vv-01363-DAT Document 95 Filed 03/02/26 Page 2 of 13
I. Background
Ms. Hiatt received the tetanus, diphtheria, and acellular pertussis (“Tdap”) and human
papillomavirus (“HPV”) vaccines on February 16, 2017, with no documented adverse reaction in
the days immediately following. (Petition (“Pet.”) at 1, ECF No. 1; Pet’r’s Medical Records
(“Pet’r’s Ex.”), ECF No. 6). Eleven days later, she sought medical care reporting chest and back
pain, jaw discomfort, and upper-respiratory symptoms, which her providers attributed to
non-cardiac and infectious causes rather than any post-vaccination process. (Pet’r’s Ex. 5 at 95,
ECF No. 6-5). Over the next several days, her symptoms evolved, and by March 1, she reported
new weakness and numbness, along with a history of gastrointestinal illness that she had not
mentioned during her earlier medical encounters. (Pet’r’s Ex. 1 at 39–42, ECF No. 6-1). As her
condition progressed, Ms. Hiatt was hospitalized with worsening weakness and sensory deficits,
ultimately receiving a diagnosis of Guillain–Barré syndrome (“GBS”) supported by absent
reflexes and elevated cerebrospinal fluid protein.1 (Pet’r’s Ex. 9 at 26–27, 55, ECF No. 6-9). She
required intensive care, intubation, intravenous immune globulin, and subsequent inpatient
rehabilitation, gradually improving by April 2017 but continuing to experience residual
symptoms. (Id. at 65). Ms. Hiatt initiated this action on September 6, 2019, alleging that the
Tdap and HPV vaccines caused the persistent injuries for which she seeks compensation.2 (Pet.
at 2; Pet’r’s Mot. for Review at 1–2).
The Special Master resolved Ms. Hiatt’s case on the written record with no evidentiary
hearing.3 (Entitlement Decision at 1 (“I determined that this matter could be fairly resolved via
ruling on the record, and both sides filed briefs in support of their positions.”), ECF No. 82). In
his Decision, the Special Master recounted the relevant factual and procedural background,
drawing on the medical records from the key period, medical literature, and the parties’ expert
reports. (See id. at 2–12). He ultimately found that Ms. Hiatt had not carried her burden to prove
causation. (Id. at 26).
Specifically, the Special Master determined that a petitioner alleging that the Tdap
vaccine caused GBS must present evidence tied to the components of the Tdap vaccine and must
show that the vaccine likely—not merely plausibly—caused the condition. (Entitlement Decision
at 24). He determined that the recent publications discussing Tdap-related treatment precautions
provided minimal and largely inapposite support, as those precautions concern individuals who
previously developed GBS after Tdap, which is not the case here, and the cited materials were
1 GBS is “a rare disorder in which your body’s immune system attacks your nerves. Weakness
and tingling in your hands and feet are usually the first symptoms. . . .” Gamboa-Avila v. Sec’y of
Health & Hum. Servs., 170 Fed. Cl. 441, 443 (2024) (citation omitted).
2 In her later briefing, Ms. Hiatt narrowed the claim to focus exclusively on the Tdap vaccine.
(Entitlement Decision at 1).
3 Hiatt v. Sec’y of Health & Hum. Servs., No. 19-1363V, 2025 WL 3230494, at *1 (Fed. Cl. Oct.
24, 2025) (docketed at ECF No. 82). For consistency with the parties’ briefing, the Court refers
to this decision as “Entitlement Decision” and cites to the page numbers of the docketed version.
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equivocal. (Id.). He likewise rejected the argument that the government had conceded causation,
explaining that current federal commentary on the Tdap–GBS pipeline reflects neutrality rather
than an affirmative causal acknowledgment. (Id. at 24–25). Ultimately, the Special Master found
that Ms. Hiatt’s causation theory contained too many substantive deficiencies to satisfy the
preponderance of the evidence standard. (Id. at 26).
II. Analysis
Ms. Hiatt seeks review of the Special Master’s decision and raises four principal
objections. First, she contends that the Special Master erred in his fact-finding with respect to her
Althen prong-one showing. (Pet’r’s Mot. for Review at 6–10 (citing Althen v. Secretary of Health
& Human Services, 418 F.3d 1274 (Fed. Cir. 2005)). Second, she argues that the Special Master
made findings not supported by the evidentiary record, thereby violating her due-process rights.
(Id. at 10–11). Third, she asserts that the decision improperly required her to present evidence
approaching scientific certainty. (Id. at 11–13 (citing Knudsen v. Secretary of Health & Human
Services, 35 F.3d 543, 548–49 (Fed. Cir. 1994)). Finally, she maintains that the Special Master
impermissibly heightened her burden of proof by demanding that she “preponderantly establish[]
that the Tdap vaccine can cause GBS.” (Id. at 13–19).
The Secretary responds that Ms. Hiatt’s objections lack merit. He first argues that the
Special Master applied the correct legal standard, emphasizing that the Vaccine Act and
longstanding Federal Circuit precedent make clear that Althen prong one requires proof by a
preponderance of the evidence. (Sec’y’s Resp. at 6, ECF No. 90). He further maintains that the
Special Master acted well within his discretion in finding that the government had not conceded
a causal association between the Tdap vaccine and GBS, and that this determination was neither
arbitrary nor capricious. (Id. at 11). The Secretary also disputes Ms. Hiatt’s claim that the Special
Master demanded scientific certainty, noting that the decision expressly applied the correct,
flexible framework. (Id. at 13). Finally, he contends that Ms. Hiatt’s due-process rights were not
violated. (Id. at 13–14). For the reasons stated herein, the Court denies Ms. Hiatt’s Motion and
sustains the Special Master’s decision.
A. Standard of Review
To obtain compensation under the Vaccine Program, a petitioner must establish either:
(1) that they sustained an injury listed on the Vaccine Injury Table (“Table Injury”) associated
with one of the administered vaccines and occurring within the statutorily defined time frame; or
(2) that their condition was caused-in-fact by a vaccine, constituting a “Non-Table Injury.” 42
C.F.R. § 100.3; 42 U.S.C. § 300aa-11(c)(1)(C); see Moberly ex rel. Moberly v. Sec’y of Health &
Hum. Servs., 592 F.3d 1315, 1321 (Fed. Cir. 2010); Capizzano v. Sec’y of Health & Hum. Servs.,
440 F.3d 1317, 1320 (Fed. Cir. 2006). There is no Table claim for GBS following a
tetanus-toxoid–containing vaccine.
Because Ms. Hiatt alleged an unlisted injury, her claim was considered “Non-Table,” and
she was required to prove causation. To establish causation-in-fact for a Non-Table claim, a
petitioner must satisfy the three-part test articulated in Althen v. Secretary of Health & Human
Services. 418 F.3d 1274. Under Althen, the petitioner must show by a preponderance of the
evidence: (1) a medical theory causally connecting the vaccination and the injury; (2) a logical
3

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sequence of cause and effect demonstrating that the vaccine caused the injury in this case; and
(3) a proximate temporal relationship between the vaccination and the onset of symptoms. Id. at
1278. The test is flexible and does not require scientific certainty, but it does require a persuasive
showing on all three prongs; failure on any defeats entitlement. Moberly, 592 F.3d at 1321;
Bunting v. Sec’y of Health & Hum. Servs., 931 F.2d 867, 873 (Fed. Cir. 1991).
For both Table and Non-Table claims, the petitioner bears the burden to establish
causation by a preponderance of the evidence—a standard that requires more than conjecture or
temporal association, but less than scientific certainty. 42 U.S.C. § 300aa-13(a)(1); Cerrone v.
Sec’y of Health & Hum. Servs., 146 F.4th 1113, 1120 (Fed. Cir. 2025); Moberly, 592 F.3d at
1321. To meet it, the petitioner must present evidence that makes their theory of causation “more
likely than not” given the entire record. See Andreu ex rel. Andreu v. Sec’y of Dep’t of Health &
Hum. Servs., 569 F.3d 1367, 1382 (Fed. Cir. 2009) (holding that “the totality of the evidence—
including the striking temporal connection between the vaccine and [petitioner’s] initial seizure,
the testimony of treating physicians, and the biologic and scientific plausibility of [petitioner’s
expert’s] theory of causation—[was] sufficient to meet the Vaccine Act’s preponderant evidence
standard”). This burden remains with the petitioner throughout the case, and it is not satisfied by
showing that a vaccine could cause the alleged injury in the abstract. See RCFC Section 13(a)(1);
W.C. v. Sec’y of Health & Hum. Servs., 704 F.3d 1352, 1356 (Fed. Cir. 2013) (citations omitted).
Rather, the petitioner must demonstrate causation as applied to their individual circumstances,
and that showing must rest on a sound and reliable medical or scientific explanation. Knudsen,
35 F.3d at 548.
On a motion for review, the Court applies the arbitrary and capricious standard to factual
findings and reviews all legal conclusions de novo. Munn v. Sec’y of Health & Hum. Servs., 970
F.2d 863, 870 n.10 (Fed. Cir. 1992). When the Court reviews mixed questions of law and fact, it
must determine whether answering it primarily involves legal or factual work. Nieves v. Sec’y of
Health & Hum. Servs., 167 Fed. Cl. 422, 428 (2023) (citing U.S. Bank Nat. Ass’n ex rel.
CWCapital Asset Mgmt. LLC v. Vill. at Lakeridge, LLC, 583 U.S. 387 (2018)). It is not this
Court’s role to reassess the evidence or substitute its own de novo factual determinations. 42
U.S.C. § 300aa-12(e); Lampe v. Sec’y of Health & Hum. Servs., 219 F.3d 1357, 1360 (Fed. Cir.
2000). Instead, the Court applies a highly deferential standard: it may set aside a Special
Master’s findings of fact only if they are arbitrary, capricious, an abuse of discretion, or
otherwise not in accordance with law. Cucuras v. Sec’y of Dep’t of Health & Hum. Servs., 26 Cl.
Ct. 537, 541 (1992), aff’d, 993 F.2d 1525 (Fed. Cir. 1993). The Court cannot “substitute its
judgment for that of the Special Master merely because it might have reached a different
conclusion.” Snyder v. Sec’y of Dep’t of Health & Hum. Servs., 88 Fed. Cl. 706, 718 (2009). A
Special Master’s determinations are upheld so long as they are “supported by evidence that is not
wholly implausible.” Hibbard v. Sec’y of Health & Hum. Servs., 698 F.3d 1355, 1363 (Fed. Cir.
2012) (quoting Cedillo v. Sec’y of Health & Hum. Servs., 617 F.3d 1328, 1338 (Fed. Cir. 2010)).
B. Objection 2: Due Process Violation
The Court begins by addressing Ms. Hiatt’s assertion that the Special Master violated her
due process rights. The argument is meritless and fails to engage with the limits of this Court’s
jurisdiction or the governing standard of review. Ms. Hiatt contends that the Special Master
made unrequested factual findings on an issue she did not present, thereby denying her due
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process. (Pet’r’s Mot. for Review at 17–18). This argument principally relates to the Special
Master’s findings in a prior case and their application here. In Kaczerowski v. Secretary of
Health & Human Services, the same Special Master considered the same expert, the same body
of medical literature, and materially similar arguments. See No. 21-758V, 2025 WL 2798865, at
*29–38 (Fed. Cl. Spec. Mstr. Aug. 28, 2025). In discussing Kaczerowski, the Special Master
noted that “the wild‑analogs to the Tdap vaccine components have not been shown to be
associated with GBS (for example, a tetanus wild bacterial infection).” (Entitlement Decision at
25 (citing 2025 WL 2798865, at *33–34)). Ms. Hiatt argues that this statement is erroneous
because she did not advance an argument concerning wild analogs. (Pet’r’s Mot. for Review at
10–11).
Ms. Hiatt misrepresents the function of that portion of the decision. The Special Master
was not making an independent factual finding about Ms. Hiatt’s case; he was summarizing the
reasoning and conclusions reached in Kaczerowski as part of his broader discussion of how
similar causation theories have been evaluated. (Entitlement Decision at 25). The summary
necessarily touched on points specific to Kaczerowski. The Special Master did not adopt those
findings, relying only on the portions relevant here. His reference to wild-analogs was merely
descriptive of the prior decision, not a factual finding about Ms. Hiatt.
Providing a summary of a related case is not arbitrary or capricious. While prior
decisions are not binding, it is neither unusual nor improper that the Special Master’s reasoning
in a prior case informed his analysis. See Davis v. Sec’y of Health & Human Servs., 94 Fed. Cl.
53, 65 (2010), aff’d, 420 F. App’x 973 (Fed. Cir. 2011) (“It is axiomatic that [S]pecial [M]asters
in vaccine cases have great leeway in building a record for decision.”). Judges and Special
Masters routinely draw on their prior evaluations of recurring experts, studies, and theories,
particularly when the evidentiary presentations substantially overlap. See Snyder, 88 Fed. Cl. at
717 (“[T]his Court has recognized the unique ability of Special Masters to adjudge cases in the
light of their own acquired specialized knowledge and expertise.”). Doing so promotes
consistency and coherence in adjudication, while still requiring each case to be decided on its
own record. Far from suggesting a due process concern, reliance on prior understanding reflects
the ordinary and legitimate effort to apply consistent reasoning to similar evidence.
Further, accepting Ms. Hiatt’s premise arguendo, allegations that a judicial officer
considered evidence she did not emphasize, misweighed the record, or articulated the governing
standards incorrectly do not, without more, amount to a constitutional violation. The Vaccine Act
provides a comprehensive and exclusive mechanism for addressing precisely these types of
objections: factual findings are reviewed for arbitrariness, and legal conclusions for correctness.
See 42 U.S.C. § 300aa-12(e). A litigant’s disagreement with how a Special Master evaluated the
record—or that the Special Master addressed an issue the petitioner did not argue—fits squarely
within that statutory review scheme. Due process does not transform routine claims of
evidentiary or legal error into constitutional injuries. See DeShaney v. Winnebago Cnty. Dep’t of
Soc. Servs., 489 U.S. 189, 200 (1989) (explaining that due process protections are triggered by
deprivations of liberty, not by alleged failures in decision-making or protection from harm). Any
genuine due‑process claim would have to be pursued through the appropriate constitutional
channels, not by reframing ordinary disagreements with the Special Master’s reasoning as a basis
for overturning the decision. Arguments of this sort are not merely unavailing; they impose
unnecessary burdens on the Court’s limited resources. When parties pursue claims that lack any
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legal foundation and fall outside the Court’s proper role, they needlessly complicate proceedings
and impede the efficient resolution of cases. Within the Vaccine Act’s tightly drawn review
structure, Ms. Hiatt’s due‑process theory does not supply a ground for disturbing the judgment.
C. Objections 1, 3, & 4: Application of Althen Prong One
Ms. Hiatt’s remaining objections relate to how the Special Master evaluated the first
prong of Althen—whether she preponderantly showed a medical theory causally connecting the
vaccination and the injury. (Pet’r’s Mot. for Review at 6–10 (Objection 1), 11–13 (Objection 3),
13–19 (Objection 4)). “Althen makes clear that a claimant’s theory of causation must be
supported by a ‘reputable medical or scientific explanation.’” Andreu, 569 F.3d at 1379 (quoting
Althen, 418 F.3d at 1278). Whether a theory of causation is “reputable” can depend on the
scientific evidence. Id. at 1380. But medical studies and data “must be viewed . . . not through
the lens of the laboratorian, but instead from the vantage point of the Vaccine Act’s preponderant
evidence standard,” which does not require “scientific certainty” or disproving “every possible
ground of causation.” Id. (citation omitted); see Broekelschen v. Sec’y of Health & Hum. Servs.,
618 F.3d 1339, 1345 (Fed. Cir. 2010); Moberly, 592 F.3d at 1325. Ms. Hiatt was therefore “not
required to present proof of causation to the level of scientific certainty,” Moberly, 592 F.3d at
1324, or to “provide conclusive evidence in the medical literature,” Andreu, 569 F.3d at 1377.
Nor was she required to support her claim with “identification and proof of specific biological
mechanisms.” Knudsen, 35 F.3d at 549. Rather, “causation can be found in vaccine cases based
on epidemiological evidence and the clinical picture.” Id. (citation omitted). It is under this
standard that the Court considers Ms. Hiatt’s remaining objections.
i. The Special Master did not err in his factual findings regarding precautions.
Ms. Hiatt’s first objection is that the Special Master’s finding that government warnings
linking tetanus vaccines to GBS do not apply to her fails both the plausibility and rational-basis
standards. (Pet’r’s Mot. for Review at 6 (referring to Entitlement Decision at 24)). She argues
this conclusion is especially flawed given a recent decision by this Court holding that similar
warnings meet those standards. (Id.). The Secretary responds that the Special Master carefully
weighed the evidentiary record, reached a supportable inference concerning the warnings at
issue, and articulated a reasoned basis for his determination. (Sec’y’s Resp. at 11–12). The Court
finds no error.
To support her theory that tetanus-toxoid–containing vaccines can cause GBS, Ms. Hiatt
relied on the expert report of Dr. Carlo Tornatore, neurologist. (Pet’r’s Ex. 36, ECF No. 56-1).
Dr. Tornatore cited two U.S. Department of Health and Human Services publications: the
Advisory Committee on Immunization Practices (“ACIP”) General Best Practice Guidelines for
Immunization and 2018 Center for Disease Control (“CDC”) Morbidity and Mortality Weekly
Report. (Pet’r’s Ex. 38, ECF No. 56-3; Pet’r’s Ex. 39, ECF No. 56-4). According to Dr.
Tornatore, both documents caution against giving a Tdap-related vaccine to anyone who
developed GBS within six weeks of a prior tetanus-toxoid dose. (Pet’r’s Ex. 36 at 12). Ms. Hiatt
characterizes this occurrence as a “challenge-rechallenge,” a recurrence pattern that can indicate
an exposure is causing an adverse reaction; she maintains that this is sufficient to show that the
Tdap vaccine may cause GBS. (Pet’r’s Mot. for Review at 8); see Capizzano, 440 F.3d 1322
(defining rechallenge). The Special Master rejected this argument. (Entitlement Decision at 23).
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Ms. Hiatt’s overarching position is that if a tetanus vaccine can cause GBS in others, it is
axiomatic that it could cause GBS as a matter of general causation, even if the recipient has not
previously had a GBS reaction. (Pet’r’s Mot. for Review at 10). She contends that the Special
Master disregarded this straightforward principle and that his contrary conclusion necessarily
lacks a rational basis. (Id.). The Special Master acknowledged that the precaution lends some
support to Ms. Hiatt’s theory. (Id. at 24). Still, he concluded that it was too slight and too
unrelated to the circumstances here to be of meaningful help. (Id. (“[T]his precaution provides
some support for Petitioner’s causation theory—but it is ultimately too flimsy and irrelevant to
the facts of this case to aid Petitioner all that much.”)). This conclusion came after analysis of the
Secretary’s immunologist expert, Dr. Olajumoke Fadugba’s, report. (Id. at 9–10). Dr. Fadugba
maintained that the precaution regarding administration of Tdap to individuals who previously
developed GBS after a tetanus-toxoid–containing dose expressly acknowledged that the evidence
of causality—either for or against—was insufficient, and that passive-surveillance data had not
suggested otherwise. (Id. at 10). Dr. Fadugba further maintained that the precaution did not
embody any reliable causal finding but instead represented a conservative advisory based on a
handful of case reports and limited to narrow circumstances. (Id. at 14).
In further support of her position that common sense indicates Tdap can cause GBS, Ms.
Hiatt relies on cases where a special master found, and was affirmed, that evidence of a
challenge-rechallenge pattern in other vaccine recipients could constitute proof of general
causation under Althen prong one. (Pet’r’s Mot. for Review at 9–10 (referring to Mohamad v.
Sec’y of Health & Hum. Servs., No. 16-1075, 2024 WL 4943421, at *7 (Fed. Cl. Nov. 12, 2024),
appeal dismissed, No. 2025-1370, 2025 WL 1341189 (Fed. Cir. May 8, 2025)). In Mohamad, the
Special Master’s conclusion that Althen prong one was met turned on findings that were
expressly tied to the evidentiary record and expert testimony presented in that case. Mohamad v.
Sec’y of Health & Hum. Servs., No. 16-1075V, 2022 WL 711604, at *17 (Fed. Cl. Jan. 27,
2022). In the Entitlement Decision for Ms. Hiatt, the Special Master distinguished Mohamad by
explaining that the holding there rested on what he understood to be the government’s effective
concession of Althen prong one, informed by the manner in which the specific precautions
interacted with the case‑specific facts and credibility findings. (Entitlement Decision at 23 (citing
Mohamad, 2022 WL 711604, at *13–15)).
The Court acknowledges that there is a divergence in how the Office of Special Masters
evaluates medical evidence concerning an alleged causal relationship between the Tdap vaccine
and GBS. See e.g., K.A. v. Sec’y of Health & Hum. Servs., 164 Fed. Cl. 98, 124 (2022)
(sustaining SM Corcoran’s decision finding no causal relationship), aff’d, No. 2023-1315, 2024
WL 2012526 (Fed. Cir. May 7, 2024); Dennington v. Sec’y of Health & Hum. Servs., No. 18-
1303V, 2023 WL 2965239 (Fed. Cl. Spec. Mstr. Apr. 17, 2023) (finding no causal relationship)
(Corcoran), mot. for review den’d, 167 Fed. Cl. 640 (2023), appeal dismissed, No. 2024-1214,
2024 WL 1255318 (Fed. Cir. Mar. 25, 2024); Montgomery v. Sec’y of Health & Hum. Servs.,
No. 15-1037V, 2019 WL 2511352 (Fed. Cl. Spec. Mstr. May 21, 2019) (finding no causal
relationship) (Moran); Rupert v. Sec’y of Health & Hum. Servs., No. 10-160V, 2014 WL 785256,
at *9 (Fed. Cl. Feb. 3, 2014) (finding no causal relationship) (Dorsey); Tompkins v. Sec’y of
Health & Hum. Servs., No. 10-261V, 2013 WL 3498652 (Fed. Cl. Spec. Mstr. June 21, 2013)
(finding no causal relationship) (Vowell), mot. for review den’d, 117 Fed. Cl. 713 (2014); but see
Winkler v. Sec’y of Health & Hum. Servs., 88 F.4th 958, 967 n.3 (Fed. Cir. 2023) (affirming SM
Dorsey’s assumption that petitioner provided a “‘proven a sound and reliable causal mechanism’
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linking . . . receipt of the Tdap vaccine to the development of GBS so as to satisfy Althen prong
one.”); Harris v. Sec’y of Health & Hum. Servs., No. 18-944V, 2023 WL 2583393, at *23 (Fed.
Cl. Feb. 21, 2023) (finding a causal relationship) (Horner); Mohamad, 2022 WL 711604, at *17
(Fed. Cl. Jan. 27, 2022) (finding a causal relationship) (Moran), review denied, decision aff’d,
No. 16-1075, 2024 WL 4943421 (Fed. Cl. Nov. 12, 2024); Swaiss v. Sec’y of Health & Hum.
Servs., No. 15-286V, 2019 WL 6520791, at *27 (Fed. Cl. Nov. 4, 2019) (finding causal
relationship) (Gowen). Some decisions have found that petitioners met their burden under Althen
based on the particular expert testimony and record presented, while others, often on materially
different records, have concluded that the evidence was insufficient to establish causation.
(Entitlement Decision at 18). The Special Master acknowledged this rift in his Entitlement
Decision. (Id. at 22).
The existence of differing outcomes does not signal a recognized causal association
between Tdap and GBS, nor does it create a binding precedent that would compel a Special
Master to reach a particular conclusion in any given case. See Boatmon v. Sec’y of Health &
Hum. Servs., 941 F.3d 1351, 1358 (Fed. Cir. 2019) (“[a] Special Master is not bound to follow
the opinions of other Special Masters.”). This variation reflects the fact-specific nature of
Vaccine Act adjudication, not a settled legal or scientific consensus in either direction. Special
Masters are charged with weighing the evidence before them, assessing the credibility of
competing experts, and applying the Althen framework to the unique factual record of each
petition. Snyder, 88 Fed. Cl. at 717. That some Special Masters have found causation on certain
records while others have not underscores that these determinations turn on the strength and
coherence of the evidence presented, not on any uniform view within the Office of Special
Masters about Tdap and GBS. Knudsen, 35 F.3d at 548 (“[c]ausation in fact under the Vaccine
Act is . . . based on the circumstances of the particular case.”); (see Entitlement Decision at 22).
Ms. Hiatt also notes in her Motion for Review that Mohamad was later sustained by
another judge of this Court. (Pet’r’s Mot. for Review at 9–10 (citing Mohamad, 2024 WL
4943421, at *9 (Hadji, J.))). Ms. Hiatt emphasizes that this affirmance went unmentioned in the
Entitlement Decision, a silence she believes understates the significance of the case.4 (Id. at 10).
This Court affirmed that evidence of the “rechallenge” paradigm in other vaccine recipients can
constitute proof of general causation under Althen prong one. Mohamad, 2024 WL 4943421, at
*9 n.10. That ruling merely illustrates why the Special Master’s analysis was not arbitrary or
capricious—it does not establish that the challenge-rechallenge paradigm is itself a legally
required or sufficient showing under Althen. Stated differently, the fact that such evidence can
satisfy an evidentiary burden does not mean that it invariably does. The arbitrary-and-capricious
standard lives a double life; it necessarily allows for divergent but reasonable outcomes. The
question is not whether another decision might also have been reasonable, but whether the one
reached is within the bounds of rational decision-making. Provided the Special Master has
4 As a general rule, the Special Master was not required to discuss that case as it constitutes non-
binding precedent. Boatmon v. Sec’y of Health & Hum. Servs., 941 F.3d 1351, 1358 (Fed. Cir.
2019); see also Hanlon v. Sec’y of Health & Human Servs., 40 Fed. Cl. 625, 630 (1998),
(“Special masters are neither bound by their own decisions nor by cases from the Court of
Federal Claims[.]”) aff’d, 191 F.3d 1344 (Fed. Cir. 1999).
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considered the evidence and articulated a rational basis for his conclusions, the mere possibility
that another adjudicator might have decided the matter differently does not render the decision
unlawful. See Hines ex rel. Sevier v. Sec’y of Dep’t of Health & Hum. Servs., 940 F.2d 1518,
1528 (Fed. Cir. 1991) (“If the [S]pecial [M]aster has considered the relevant evidence of record,
drawn plausible inferences and articulated a rational basis for the decision, reversible error will
be extremely difficult to demonstrate.”). Although Mohamad was sustained, that outcome does
not determine whether Ms. Hiatt has met her burden, and its affirmance does not justify remand
or reversal.
That the Department of Health and Human Services issued precautions that apply only to
individuals who previously developed GBS after a tetanus-toxoid dose was a central aspect of
the Special Master’s reasoning. (See Entitlement Decision at 24). The Secretary argued that,
despite the government publications, the warnings from the ACIP and CDC could not advance
Ms. Hiatt’s Althen prong-one theory because she had no history of GBS following an earlier
tetanus-containing vaccination. (Sec’y’s Resp. at 12). Accepting that argument, the Special
Master captured the point succinctly: the precaution “was inapplicable to Ms. Hiatt, who had not
been shown to have previously experienced post-Tdap vaccine GBS.” (Entitlement Decision at
14). In examining cases where a causal relationship was found, the Special Master found those
decisions distinguishable because they involved either effective concessions on Althen prong one
or case-specific credibility assessments that are absent here. (Id. at 24). Although the precautions
reasonably lend support to Ms. Hiatt’s position that Tdap may, in some circumstances, be
associated with GBS, a precaution remains just that—a conservative measure rather than an
admission of causation. The Special Master’s conclusion that these warnings do not establish that
Tdap can cause GBS, particularly when evaluated against the record, reflects a reasoned
assessment of their limited probative value and therefore cannot be deemed arbitrary.
ii. The Special Master did not require proof of scientific certainty.
The Court is also not persuaded by Ms. Hiatt’s claim that the Special Master required
proof of scientific certainty in contravention of legal precedent. Ms. Hiatt argues that the Special
Master’s findings demonstrate that he applied an improperly heightened burden of proof. (Pet’r’s
Mot. for Review at 10–11 (referring to statements that “epitope similarity was too nonspecific,”
that there was “no evidence that Petitioner possessed cross‑reactive antibodies,” and that there
was no “epidemiologic evidence”) (citing Entitlement Decision at 6, 11))). According to Ms.
Hiatt, these expectations collectively amount to a requirement of near‑definitive mechanistic
proof, far beyond what the preponderance of the evidence standard requires. (Id. at 11).
The Secretary contends, and the Court agrees, that although Ms. Hiatt frames her
objection as a legal challenge, it amounts to a disagreement with the Special Master’s weighing
of the expert evidence and a misunderstanding of his findings. (Sec’y’s Resp. at 13). The
passages on which Ms. Hiatt relies are not findings or legal conclusions at all; they are
summaries of the expert reports. Section II of the Decision serves only to recount the parties’
submissions, not to resolve them. (Entitlement Decision at 3–12). When a decision simply
recounts the contents of an expert report without adopting or analyzing its conclusions, that
recitation functions as dicta rather than a finding of fact. See Obiter Dictum, BLACK’S LAW
DICTIONARY (12th ed. 2024) (“A judicial comment made while delivering a judicial opinion, but
one that is unnecessary to the decision in the case and therefore not precedential (although it may
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be considered persuasive).”); Co-Steel Raritan, Inc. v. Int’l Trade Comm’n., 357 F.3d 1294, 1307
(Fed. Cir. 2004) (“Because statements made in dicta do not implicate the substantive holding of
the case, they cannot be considered binding authority.”) (internal quotations omitted). Treating
those summaries as if they reflected the Special Master’s own determinations misapprehends the
structure of the Decision and obscures the actual findings that appear later in the analysis.
Because Ms. Hiatt’s argument is premised on a misreading of the Special Master’s findings, it is
unavailing.
To the extent Ms. Hiatt invites the Court to reweigh the evidence, that invitation must be
declined. See Lampe, 219 F.3d at 1360. While the Special Master “must review record evidence
to assess the preponderance standard,” he is “at liberty to determine the weight of each piece of
evidence.” Faulkenberry v. Sec’y of Health and Human Servs., 176 Fed. Cl. 700, 707 (2025)
(citations omitted). That said, a causation theory must only be “legally probable, not medically or
scientifically certain.” Knudsen, 35 F.3d at 549. A review of the Entitlement Decision confirms
that the Special Master did not demand scientific certainty or impose an unduly rigorous burden
of proof. Instead, he evaluated the evidence Ms. Hiatt submitted and found it insufficient under
the preponderance standard. His observations regarding epitope similarity, cross-reactive
antibodies, and epidemiologic data, (Entitlement Decision at 6, 11), reflected an assessment of
the strength of Ms. Hiatt’s theory, not the imposition of inflexible legal prerequisites. Based on
the record, the Special Master reasonably determined that Ms. Hiatt had not met her burden
under Althen without requiring definitive scientific proof of causation.
iii. The Special Master did not heighten the burden of proof.
Finally, Ms. Hiatt contends that the Special Master improperly elevated the standard
under Althen prong one by requiring not merely a “reputable” medical theory, but affirmative
proof that the vaccine can cause the alleged injury. (Pet’r’s Mot. for Review at 13). Ms. Hiatt
states that this approach effectively disregards the long-recognized principle that a petitioner may
satisfy prong one by presenting a biologically plausible theory, proven by a preponderance of the
evidence. (Id. at 13–14). She argues that the standard applied exceeds what is legally required
and imposes a burden unattainable under current scientific understanding. (Id. at 14). The
Secretary reasons that the Special Master applied the correct preponderance standard. (Sec’y’s
Resp. at 6). The Court finds that while a biologically plausible theory is a necessary component
of a petitioner’s case, it must be substantiated by reliable evidence that, taken as a whole,
establishes causation by a preponderance of the evidence; the Special Master did not misapply
this standard.
Ms. Hiatt appears to treat the biologically plausible medical theory and the
preponderance of the evidence standard as distinct and independent requirements. They are not.
In vaccine injury cases, the preponderance of the evidence standard and the requirement of a
biologically plausible medical theory under Althen prong one work together to define both the
nature and degree of proof a petitioner must provide to establish causation. See 42 U.S.C. §
300aa13(a)(1); Althen, 418 F.3d at 1280. The biologically plausible theory sets the framework: it
must offer a scientifically credible explanation for how the vaccine could cause the alleged
injury. Knudsen, 35 F.3d at 549. This theory need not be universally accepted or proven to a
scientific certainty; rather, it must be grounded in reliable medical or scientific principles and
rise above mere speculation. Id. Once such a theory is articulated, the petitioner must then prove
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it by a preponderance of the evidence—that is, show it is more likely than not that the vaccine
caused the injury. White v. Sec’y of Health & Hum. Servs., ___ F. 4th. ___, 2025 WL 3703259,
at *4 (Fed. Cir. Aug. 27, 2025) (citing Lobo v. Dep’t of Just., 139 F.4th 1311, 1317 (Fed. Cir.
2025) (noting that “‘medical certainty’ . . . is more demanding than the preponderance standard
of more likely than not”)). This evidentiary standard allows for flexibility, recognizing that direct
proof is often unavailable in complex medical cases. Althen, 418 F.3d at 1279. Circumstantial
evidence, expert opinion, and logical inference may suffice. Id. at 1280. Together, these
standards ensure that petitioners are not held to an unattainable scientific threshold, while still
requiring a rational and persuasive showing of causation based on the specific facts of the case.
Put simply, plausibility must be proven by a preponderance of the evidence.
Ms. Hiatt correctly observes that Althen prong one is satisfied by presenting a
biologically plausible medical theory, so long as that theory is supported by reliable evidence,
which may include circumstantial proof. (Pet’r’s Mot. for Review at 14). She argues that the
Special Master departed from this standard by effectively requiring her to demonstrate that the
Tdap vaccine actually “can cause” GBS, a level of proof she describes as scientifically
unattainable. (Id.). Notably, however, Ms. Hiatt herself characterizes Althen prong one in nearly
identical terms earlier in her Motion for Review, stating that prong one “asks a Petitioner to
show that a vaccine can cause, (general causation), an injury.” (Id. at 10 (emphasis in original)).
In the end, it is difficult to discern any meaningful distinction between the standard Ms. Hiatt
advocates and the one she criticizes the Special Master for applying.
In addressing the evidentiary standard under the first Althen prong, the Federal Circuit
has repeatedly made clear that it is not enough for a petitioner to present a causation theory that
is merely scientifically or medically plausible. See Cerrone, 146 F.4th at 1121 (rejecting the
notion that plausibility alone satisfies prong one); Kalajdzic v. Sec’y of Health & Hum. Servs.,
No. 2023-1321, 2024 WL 3064398, at *2 (Fed. Cir. June 20, 2024) (reaffirming that arguments
advocating “a less than preponderance standard” are “plainly inconsistent with [Circuit]
precedent” (citing Moberly, 592 F.3d at 1322)); Boatmon, 941 F.3d at 1359 (emphasizing that
plausibility must be supported by reliable evidence). While a petitioner must present a
biologically plausible medical theory explaining how the vaccine could cause the alleged injury,
that theory must also be supported by evidence sufficient to meet the preponderance of the
evidence standard. Knudsen, 35 F.3d at 548–49 (the standard of proof for causation under the
Vaccine Act is “probable” and “preponderance”).
Despite Ms. Hiatt’s assertions, a theory alone is insufficient to satisfy the burden under
Althen prong one. (Pet’r’s Mot. for Review at 15–16). The theory is the starting point, as it
defines what the petitioner is trying to prove. But the petitioner must also provide some support
that the theory is plausible in the context of the case. Assessment of that theory “is made through
the standards of the Vaccine Act’s preponderance evidence test, not through the standards of
rigorous medical research[.]” Doles v. Sec’y of Health & Hum. Servs., No. 2023-2404, 2025 WL
1177875, at *3 (Fed. Cir. Apr. 23, 2025) (citing Andreu, 569 F.3d at 1380). The Special Master
then evaluates the quality, reliability, and coherence of that evidence. Burns v. Sec’y of Health &
Hum. Servs., 3 F.3d 415, 417 (Fed. Cir. 1993) (noting that a special master has discretion to
determine the relative weight of the evidence, including medical records). Thus, a theory without
some level of satisfactory evidentiary support is insufficient. The petitioner must bridge the gap
between theory and proof with persuasive evidence tailored to the facts of the case. Exum v.
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Sec’y of Health & Hum. Servs., 178 Fed. Cl. 627, 650 (2025) (affirming Special Master’s
requirement that the petitioner must “knit[ ] together . . . an overall theory that does not amount
to speculation or unreasonable extrapolation.”). As the Federal Circuit recently affirmed, “the
evidence a claimant offers must, in totality, always accomplish one thing in the end:
preponderantly establish that the vaccine(s) at issue more likely than not can cause the relevant
disease.” Cerrone, 146 F.4th at 112 (emphasis removed). In Ms. Hiatt’s case, the Special Master
correctly identified and applied the governing standard. It appears that Ms. Hiatt’s objections on
this point relate to the weight assigned to the evidence she presented, rather than the legal
framework employed by the Special Master. The Court has already found that his findings were
rational.
As part of her argument, Ms. Hiatt contends that the Federal Circuit itself has misapplied
the Althen prong one standard in recent years. (Pet’r’s Mot. for Review at 18 (referring to
Boatmon, 941 F.3d 1351 and Cerrone, 146 F.4th 1113 as “aberrant” to Althen)). She asserts that
these decisions have impermissibly elevated a petitioner’s burden by requiring definitive proof of
causation, rather than a reliable and biologically plausible theory supported by a preponderance
of the evidence. (Id.). In her view, this trend reflects a departure from the flexible evidentiary
framework that Althen was intended to preserve. (Id.). Whether Ms. Hiatt believes the Federal
Circuit has veered off course from Althen is ultimately a matter for her to raise with that court.
This Court is bound to follow the route the Circuit charts. If a course correction is warranted, it is
the Circuit—not this Court—that holds the map and the wheel.
Viewed through the deferential lens required by the Vaccine Act, Ms. Hiatt’s objections
do not warrant disturbing the Special Master’s decision. Her challenges to his fact-finding
amount to disagreements with how the evidence was weighed, not demonstrations that the
findings were improper. The record reflects a careful and transparent evaluation of the medical
records, expert reports, and competing theories. Nothing in Ms. Hiatt’s submissions identifies a
factual determination that approaches arbitrariness or caprice or a misapplication of the
governing legal standards. The decision does not suggest that the Special Master required
scientific certainty or otherwise heightened Ms. Hiatt’s burden; he applied the Althen framework
and the preponderance standard as precedent requires. Because the Court’s role is limited to
ensuring that the Special Master acted rationally and within the bounds of law, the decision must
be sustained.5
5 Ms. Hiatt requests that the Court remand this matter with instructions that it be reassigned to
Special Master Young. (Pet’r’s Mot. for Review at 20). Even assuming Ms. Hiatt had prevailed
on the merits, she has not established good cause to justify reassignment. The record lacks any
indication of bias, misconduct, or other exceptional circumstances that would warrant removal of
the Special Master. Moreover, the Court is guided by the well-established principle that litigants
do not have the right to choose their adjudicator.
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III. Conclusion
Framed against the proper standard of review, Ms. Hiatt’s objections fall short, and the
record provides no basis to disturb the Special Master’s well-supported decision. Because she
has identified no legal error and no improper factual determination that meets the threshold for
reversal, the Court DENIES her Motion for Review, (ECF No. 89), and SUSTAINS the Special
Master’s decision, (ECF No. 82). The Clerk is directed to enter judgment accordingly.
The Court has filed this ruling under seal. The parties shall confer to determine proposed
redactions to which the parties agree. Per Vaccine Rule 18(b), fourteen (14) days from the date
of this decision, the parties shall file a Joint Status Report indicating their agreement with the
proposed redactions, attaching a copy of those pages of the Court’s ruling containing proposed
redactions, with all proposed redactions clearly indicated.
IT IS SO ORDERED.
s/ David A. Tapp
DAVID A. TAPP, Judge
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