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Ischemic Stroke After Bivalent COVID-19 Vaccination: Self-Controlled Case Series Study

Stanley Xu1, Lina S Sy1, Vennis Hong1

  • 1Department of Research & Evaluation, Southern California Permanente Medical Group, Pasadena, CA, United States.

JMIR Public Health and Surveillance
|June 25, 2024
PubMed

Insights

Bivalent COVID-19 vaccination did not increase ischemic stroke risk overall. A potential increased risk was observed within 42 days for younger individuals receiving both Pfizer-BioNTech and flu vaccines, warranting further study.

Area of Science:

  • Epidemiology
  • Vaccinology
  • Neurology

Background:

  • The association between bivalent COVID-19 vaccines and ischemic stroke risk is not fully understood.
  • Existing studies have yielded uncertain conclusions regarding this potential link.

Purpose of the Study:

  • To assess the risk of ischemic stroke following bivalent COVID-19 vaccination during the 2022-2023 season.
  • Evaluate potential associations in specific subgroups and with coadministered vaccines.

Main Methods:

  • A self-controlled case series study design was employed.
  • Utilized electronic health records for ischemic stroke identification (ICD-10 codes).
  • Analyzed risk intervals of 1-21 and 1-42 days post-vaccination using conditional Poisson regression.

Main Results:

  • No increased ischemic stroke risk was found within 21 days for either vaccine.
  • An elevated risk was noted within 42 days for individuals under 65 receiving Pfizer-BioNTech and influenza vaccines concurrently.
  • Subgroup analyses revealed potential elevated risks in specific populations, though often not statistically significant after chart review.

Conclusions:

  • The study found no statistically significant increase in ischemic stroke risk associated with bivalent COVID-19 vaccination overall.
  • Further investigation is needed for specific subgroups, particularly younger individuals receiving concurrent influenza vaccination and those with prior SARS-CoV-2 infection.
  • Highlights the importance of ongoing vaccine safety surveillance, including for monovalent vaccines in the subsequent season.
Abstract

Keywords:
COVID-19SARS-CoV-2TIAadverseassociationbivalentbivalent COVID-19 vaccinecardiovascularcase seriescoadministrationcorrelationincidenceinfectiousinfluenzainfluenza vaccineischemiaischemicischemic strokerespiratoryriskrisksself-controlled case seriesside effectstrokesubgroup analysessubgroup analysistransient ischemic attackvaccinationvaccinevaccines

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