Background: This study assessed short-term stroke risk following COVID-19 vaccination using Qatar's national stroke registry and health platform.
Research design and methods: A self-controlled risk-interval study was conducted among individuals with stroke post-COVID-19 vaccination between 1 December 2020, and 11 April 2023. Stroke incidence during risk windows (0-21 and 22-42 days post-vaccination) was compared to a control window (43-180 days).
Results: Among 3,070 stroke cases, 685 met inclusion criteria. Stroke incidence was elevated in the 0-21-day window (IRR: 1.32; 95% CI: 1.07-1.63), but not in the 22-42-day window (IRR: 1.03; 95% CI: 0.82-1.30). Excess risk was estimated at 0.55 (95% CI: -0.04 to 1.01) strokes per 100,000 vaccine doses. IRRs for the 0-21-day window were 1.39 (95% CI: 1.08-1.80) for BNT162b2 and 1.15 (95% CI: 0.78-1.69) for mRNA-1273. By subtype, IRRs were 1.34 (95% CI: 1.07-1.68) for ischemic stroke, 1.11 (95% CI: 0.58-2.11) for hemorrhagic stroke, and 1.46 (95% CI: 0.38-5.56) for cerebral venous sinus thrombosis.
Conclusion: A small, transient increase in stroke incidence was observed within 21 days of vaccination; however, such events remain exceedingly rare, with an estimated excess risk substantially lower than that typically associated with infection.
Keywords: Adverse event; hemorrhagic; immunization; ischemic; mRNA; risk; thrombosis; vaccine.