TOPLINE:
Receipt of the bivalent COVID-19 vaccine was not associated with an increased stroke risk in the first 6 weeks after vaccination with either the Pfizer or Moderna vaccines, a new study of Medicare beneficiaries showed.
METHODOLOGY:
- The analysis included 5.4 million people age ≥ 65 years who received either the Pfizer-BioNTech COVID-19 bivalent vaccine or the Moderna bivalent vaccine, or the Pfizer vaccine and a high-dose or adjuvanted concomitant influenza vaccine (ie, administered on the same day).
- A total of 11,001 of the cohort experienced a stroke in the first 90 days after vaccination.
- The main outcome was stroke risk (nonhemorrhagic stroke, transient ischemic attack [TIA], or hemorrhagic stroke) during the 1- to 21-day or 22- to 42-day window after vaccination vs the 43- to 90-day control window.
- The mean age of participants was 74 years, and 56% were female.
TAKEAWAY:
- There was no statistically significant association with either brand of the COVID-19 bivalent vaccine or any of the stroke outcomes during the 1- to 21-day or 22- to 42-day risk window compared with the 43- to 90-day control window (incidence rate ratio [IRR] range, 0.72-1.12).
- Vaccination with COVID-19 bivalent vaccine plus a high-dose or adjuvanted influenza vaccine (n = 4596) was associated with a significantly greater risk for nonhemorrhagic stroke 22-42 days after vaccination with Pfizer-BioNTech (IRR, 1.20; risk difference/100,000 doses, 3.13) and an increase in TIA risk 1-21 days after vaccination with Moderna (IRR, 1.35; risk difference/100,000 doses, 3.33).
- There was a significant association between vaccination with a high-dose or adjuvanted influenza vaccine (n = 21,345) and nonhemorrhagic stroke 22-42 days after vaccination (IRR, 1.09; risk difference/100,000 doses, 1.65).
IN PRACTICE:
"The clinical significance of the risk of stroke after vaccination must be carefully considered together with the significant benefits of receiving an influenza vaccination," the authors wrote. "Because the framework of the current self-controlled case series study does not compare the populations who were vaccinated vs those who were unvaccinated, it does not account for the reduced rate of severe influenza after vaccination. More studies are needed to better understand the association between high-dose or adjuvanted influenza vaccination and stroke."
SOURCE:
Yun Lu, PhD, of the Center for Biologics Evaluation and Research, US Food and Drug Administration, Silver Spring, Maryland, was the lead and corresponding author of the study. It was published online on March 19 in JAMA.
LIMITATIONS:
Some stroke cases may have been missed or misclassified. Additionally, the study included only vaccinated individuals — a population considered to have health-seeking behaviors — which may limit the generalizability of the findings. The study was conducted using COVID-19 bivalent vaccines, which are no longer available.
DISCLOSURES:
This work was funded by the US Food and Drug Administration through an interagency agreement with the Centers for Medicare & Medicaid Services. Lu reported no relevant financial relationships. The other authors' disclosures are listed in the original paper.