Thrombocytopenia following Pfizer and Moderna SARS‐CoV‐2 vaccination
19 February 2021
Cases of apparent secondary immune thrombocytopenia (ITP) after SARS‐CoV‐2 vaccination with both the Pfizer and Moderna versions have been reported and reached public attention. Public alarm was heightened following the death of the first identified patient from an intracranial hemorrhage, which was reported on the Internet, then in USA Today1 and then in The New York Times.2 Described below, we have collected a series of cases of very low platelet counts occurring within 2 weeks of vaccination in order to enhance our understanding of the possible relationship, if any, between SARS‐CoV‐2 vaccination and development of ITP with implications for surveillance and management.
In summary, we cannot exclude the possibility that the Pfizer and Moderna vaccines have the potential to trigger de novo ITP (including clinically undiagnosed cases), albeit very rarely. Distinguishing vaccine‐induced ITP from coincidental ITP presenting soon after vaccination is impossible at this time. Additional surveillance is needed to determine the true incidence of thrombocytopenia post vaccination. If the incidence of thrombocytopenia post vaccination is higher than that based on available case reports, we anticipate that many more cases will be reported in the coming weeks as a higher proportion of the population is vaccinated. It may be worthwhile to see whether exacerbations of other conditions considered to have an autoimmune pathophysiology occur as well to gain a better understanding of host response to vaccination.
