Blood Clots with Low Platelets Very Rare After COVID-19 Vaccination

We reviewed 13,321,570 vaccine administrations across 8,081,360 patients to see whether different vaccination types were associated with four criteria typically associated with Thrombosis with Thrombocytopenia Syndrome (TTS).^1-3 We evaluated COVID-19 vaccinated patients admitted with a venous or arterial thrombosis (clot) within 30 days after vaccination, that had a platelet count less than 110,000/µL and had an abnormal PF4 antibody.

Three of 8,081,360 patients fit all four criteria, but two of them were administered heparin which could have caused their low platelet counts. The one patient meeting all these criteria and not associated with heparin was admitted 11 days after the J&J vaccine, had a platelet count of 78,000/µL on admission, and was not on birth control. Figure 1 shows the number of patients with the cumulative factors from left to right, meaning 406 out of 4,840,616 patients (0.008%) with a Pfizer vaccine had an admission within 30 days, a thrombosis diagnoses, and a platelet count less than 110,000/µL.

Figure 1

Patients Meeting TTS-Related Criteria After Vaccination

Our analysis shows one potential Thrombotic Thrombocytopenic Syndrome (TTS) case out of 13,321,570 vaccine administrations and 8,081,360 patients.

Data are pooled from 122 organizations, representing 618 hospitals that span 50 states, with 27 million patients seen since the first emergency use authorization (EUA) for a SARS-CoV-2 vaccine. The data is from Cosmos, a HIPAA-limited data set of patient information contributed by Epic customers. Vaccination data from outside locations might not appear in our data unless the patient has an interaction with the health system. In order to include the greatest number of vaccinations, we included recent vaccinations that did not have a full 30-day elapse during our study period. This means that vaccines that have been available for longer (Moderna and Pfizer) will be comparatively more likely to have potential cases in our data than the J&J vaccine.

References

1. Joint CDC and FDA Statement on Johnson & Johnson COVID-19 Vaccine. April 13, 2021. Accessed May 7, 2021. https://www.cdc.gov/media/releases/2021/s0413-JJ-vaccine.html
2. Bussel B, et. al. Thrombosis with Thrombocytopenia Syndrome (also termed Vaccine-induced Thrombotic Thrombocytopenia). American Society of Hematology. Version 1.4. April 29, 2021. Accessed May 7, 2021. https://www.hematology.org/covid-19/vaccine-induced-immune-thrombotic-thrombocytopenia
3. D Cines, J Bussel. SARS-CoV-2 Vaccine-Induced Immune Thrombotic Thrombocytopenia. NEJM. April 16, 2021. Accessed May 10, 2021. https://www.nejm.org/doi/full/10.1056/NEJMe2106315?query=recirc_curatedRelated_article