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Cosmos Study

Stroke and Blood Clotting Disorders Rare After Monovalent and Bivalent COVID Vaccination

May 24, 2023
Dual-Team Study
Team A:Kersten Bartelt, RNJoey HaddockNeil Sandberg
Team B:Chris Alban, MDBrendan Joyce

Key Findings

  • Stroke, thrombocytopenia, or thrombosis in the 30 days after monovalent and bivalent COVID-19 vaccination are very uncommon, seen in less than 1% of patients.  
  • Patients that receive the monovalent or bivalent COVID-19 vaccine are about 9% less likely to develop a stroke, 20% less likely to develop thrombocytopenia, and 12% less likely to develop thrombosis than patients who receive the flu vaccination. 
  • The incidence of thrombocytopenia and thrombosis are more than twice as common after COVID-19 infection than after COVID-19 vaccination. 

There have been some reports of ischemic stroke in patients after COVID-19 vaccination, but CDC and FDA have noted that these risks are small and continue to recommend COVID-19 vaccination for most patients.1 Additionally, there have been contradictory observations around the risk of stroke and thrombosis related to receiving the COVID-19 vaccination.2 Because both monovalent and bivalent COVID-19 vaccinations make use of pioneering mRNA design, we wanted to compare rates of different clotting conditions following COVID-19 mRNA vaccination with those following a non-mRNA vaccination, such as the influenza vaccine.  

We evaluated the rate of new diagnoses of stroke, thrombocytopenia, and arterial and venous thrombosis after monovalent and bivalent COVID-19 vaccination and compared those to the rates of those conditions after influenza vaccination and COVID-19 infection.  

We evaluated 16,687,080 patients that had an influenza vaccination, monovalent COVID-19 vaccination, bivalent COVID-19 vaccination, or COVID-19 infection. We matched these groups on age, sex, immunization or infection year, and number of previously diagnosed chronic conditions that increase cardiovascular risk. We then determined the rate of new diagnoses of stroke, thrombocytopenia, and arterial and venous thrombosis in the 30 days following the vaccine administration or COVID-19 infection.  

We found that all four of the conditions were very rare for all the populations assessed, but were most common after COVID-19 infection, as shown in Figure 1. Stroke, thrombocytopenia, and thrombosis are more common after influenza vaccination than after the monovalent or bivalent COVID-19 vaccinations. Both COVID-19 vaccinations were nearly equivalent for all four of the cardiovascular diagnoses assessed. 

Figure 1
Cardiovascular Diagnoses After Vaccination or Infection
Cardiovascular Diagnoses After Vaccination or Infection
Figure 1. Unadjusted rates of diagnosis of cardiovascular conditions within the 30 days after vaccination or infection.

These findings align with CDC and FDA reports that these conditions after COVID-19 vaccination remain rare and suggest that bivalent and monovalent COVID-19 vaccinations have similar rates of these diagnoses after vaccination.1  

These data come from Cosmos, a HIPAA-defined Limited Data Set of more than 184 million patients from 199 Epic organizations including 1,141 hospitals and over 24,900 clinics, serving patients in all 50 states and Lebanon. This study was completed by two teams that worked independently, each composed of a clinician and research scientists. The two teams came to similar conclusions. 

References

  1. CDC. CDC & FDA identify preliminary COVID-19 vaccine safety signal for persons aged 65 years and older. Centers for Disease Control and Prevention. Published January 13, 2023. Accessed May 1, 2023. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/bivalent-boosters.html‌ 
  2. Kakovan M, Ghorbani Shirkouhi S, Zarei M, Andalib S. Stroke associated with COVID-19 vaccines. J Stroke Cerebrovasc Dis. 2022;31(6):106440. doi:10.1016/j.jstrokecerebrovasdis.2022.106440