Thrombocytopenia Following mRNA Vaccination Against SARS-CoV-2
In connection with the administration of mRNA-based vaccines against the SARS-CoV-2 coronavirus, cases of secondary immune thrombocytopenia (ITP) have been described. A commentary published by a large team of authors in the American Journal of Hematology described a series of cases of low platelet counts identified within 2 weeks of vaccination. The data was obtained from the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), the Department of Health and Human Services (HHS), and the Vaccine Adverse Event Reporting System (VAERS), as well as through direct communication with patients and their physicians.
Described Cases
Twenty cases of patients with thrombocytopenia after vaccination were found, with 17 without pre-existing thrombocytopenia, and bleeding symptoms described in 14 cases. All cases were identified as newly occurring after vaccination. The age (range 22–73 years, median 41 years) and gender (11 women and 8 men) were known for 19 of these 20 individuals. A total of 9 received the Pfizer/BioNTech vaccine and 11 the Moderna vaccine. All 20 individuals were hospitalized, and many presented with petechiae, bruising, or mucosal bleeding, with bleeding symptoms beginning 1–23 days (median 5 days) after vaccination. The platelet count at initial examination was mostly < 10 × 109/L (range 1–36 × 109/L, median 2 × 109/L).
One patient was known to have ITP in remission, one had mild thrombocytopenia in history with positive antiplatelet antibodies, one patient had a history of mild thrombocytopenia, and one had known congenital thrombocytopenia (with platelet counts between 40 and 60 × 109/L). An additional 3 patients had autoimmune diseases.
Overall, 15 cases received treatment for suspected ITP upon hospital admission, usually with corticosteroids or intravenous immunoglobulins (IVIG). In 8 cases, platelet transfusion was administered, and rituximab, vincristine, or romiplostim were used for individuals. One patient died following intracranial bleeding despite receiving IVIG, corticosteroids, rituximab, and platelet transfusions.
An additional 5 patients with thrombocytopenia were reported through VAERS, but sufficient clinical information is not available.
Possible Connections or Coincidence?
The question remains whether there is a connection between vaccination and thrombocytopenia and whether this connection is random or causal. Commentary authors note that it is not surprising that 17 possible newly occurring thrombocytopenias were described among 20 million people in the USA who received at least one dose of the mentioned vaccines by February 2, 2021. Calculations showed that the incidence of immune-mediated thrombocytopenia after SARS-CoV-2 vaccination appears to be lower or roughly comparable to coincident cases. It is also known, for example, that in children thrombocytopenia appears approximately in 1 out of 40 thousand cases following some vaccines (MMR). ITP has also been documented following the varicella vaccine or other diseases.
It is important to emphasize that except for one case of ITP after SARS-CoV-2 vaccination, all appeared after the first vaccine dose, i.e., in a relatively short time interval. Furthermore, it must be stated that mild asymptomatic cases of ITP post-vaccination likely went undetected.
Conclusion
The connection between the SARS-CoV-2 vaccine and secondary ITP is still unclear, and a possible association cannot be ruled out. At this moment, it is impossible to differentiate vaccine-induced ITP from coincidental ITP occurring shortly after vaccination based on available data. Another dimension of the problem could be the possible exacerbation of pre-existing autoimmune disease. Further monitoring focused on this issue is needed, along with data collection for better understanding of potential further connections and treatment recommendations.
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Source: Lee E. J., Cines D. B., Gernsheimer T. et al. Thrombocytopenia following Pfizer and Moderna SARS-CoV-2 vaccination. Am J Hematol 2021 May 1; 96 (5): 534−537, doi: 10.1002/ajh.26132.
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