Mayra Del Bosque v. HHS - MMR, immune thrombocytopenic purpura (ITP) (2025)

On April 27, 2020, Mayra Del Bosque, as the parent and natural guardian of M.R., a minor, filed a petition under the National Childhood Vaccine Injury Act. The petition alleged that M.R. suffered immune thrombocytopenic purpura (ITP) caused-in-fact by vaccinations received on November 7, 2017, including the measles, mumps, and rubella (MMR) vaccine.

Petitioner counsel was David John Carney of Green & Schafle LLC, and respondent counsel was Benjamin Patrick Warder of the U.S. Department of Justice.

Special Master Daniel T. Horner presided over the case.

The parties did not dispute that M.R. suffered ITP, but they disagreed on the timing of symptom onset. In a prior ruling on October 12, 2023, the Special Master found that abnormal bruising was the first symptom of M.R.'s ITP, with onset occurring no earlier than 31 days and within 42 days post-vaccination.

This timing meant the case did not qualify for the Vaccine Injury Table's presumption for ITP, which requires onset between 7-30 days post-vaccination for the MMR vaccine. Consequently, the case proceeded under the "causation-in-fact" standard, requiring petitioner to prove a medical theory connecting the vaccine and injury, a logical sequence of cause and effect, and a proximate temporal relationship (the Althen analysis).

Respondent conceded that the MMR vaccine can cause ITP and that the elevated risk persists for up to 42 days, satisfying the first and third Althen prongs. The dispute centered on the second prong: whether there was a logical sequence of cause and effect implicating the MMR vaccine.

Respondent argued that M.R.'s ITP was atypical for vaccine-caused ITP, citing an insidious and gradual decrease in platelet levels, chronicity, and the presence of pharyngitis diagnosed on December 8, 2017, as a more likely cause. Respondent's expert, Dr.

Strouse, suggested that vaccine-caused ITP typically involves a sudden decrease in platelets and is usually self-limiting, resolving within weeks to months. Dr.

Strouse also pointed to the pharyngitis as a potential cause, noting that short-term decreases in neutrophils and platelets can be seen with viral suppression. Petitioner argued that M.R.'s clinical course supported a logical sequence of cause and effect, supported by her expert, Dr.

Ghose, who opined that the MMR vaccine caused M.R.'s ITP and that no other triggering event was documented. Petitioner contended that respondent's arguments regarding gradual onset and chronicity were not persuasive, noting that respondent acknowledged that 10% of ITP patients have chronic disease and that the six-month severity requirement for compensation does not preclude chronic cases.

Petitioner also argued that the pharyngitis diagnosis was vaguely described and not attributed to M.R.'s ITP by treating physicians. The Special Master found that respondent's arguments regarding the onset and chronicity of M.R.'s ITP were not persuasive.

The Special Master noted that the medical records did not clearly indicate the speed of M.R.'s platelet drop and that the Rajantie study cited by respondent had limitations. The Special Master also found that the chronicity of M.R.'s ITP did not distinguish it from vaccine-related ITP, citing respondent's own expert's acknowledgment of chronic ITP after MMR vaccination in some cases.

Regarding the pharyngitis, the Special Master found that it was not sufficiently established as a sole cause, noting that "pharyngitis" simply indicates a sore throat and that respondent's expert relied on a syllogism that viral infections often cause ITP. The Special Master concluded that petitioner proved by a preponderance of the evidence that M.R.'s ITP was caused-in-fact by the MMR vaccination.

A separate order for damages will be issued.