Background and Objectives Acute arterial ischemic stroke (AIS) has been reported as a rare adverse event following coronavirus disease 2019 (COVID-19) vaccination with messenger RNA (mRNA) or viral vector vaccines. However, data are sparse regarding the risk of postvaccination AIS and its potential association with thrombotic-thrombocytopenia syndrome (TTS).

Methods A systematic review and meta-analysis of randomized controlled clinical trials (RCTs), pharmacovigilance registries, registry-based studies, observational cohorts, and case-series was performed with the aim to calculate the following: (1) the pooled proportion of patients presenting with AIS following COVID-19 vaccination; (2) the prevalence of AIS after mRNA and vector-based vaccination; and (3) the proportion of TTS among postvaccination AIS cases. Patient characteristics were assessed as secondary outcomes.

Results Two RCTs, 3 cohort studies, and 11 registry-based studies comprising 17,481 AIS cases among 782,989,363 COVID-19 vaccinations were included in the meta-analysis. The pooled proportion of AIS following exposure to any COVID-19 vaccine type was 4.7 cases per 100,000 vaccinations (95% CI 2.2–8.1; I² = 99.9%). The pooled proportion of AIS following mRNA vaccination (9.2 cases per 100,000 vaccinations; 95% CI 2.5–19.3; I² = 99.9%) did not differ compared with adenovirus-based vaccination (2.9 cases per 100,000 vaccinations; 95% CI 0.3–7.8; I² = 99.9%). No differences regarding demographics were disclosed between patients with AIS following mRNA-based or vector-based vaccination. The pooled proportion of TTS among postvaccination AIS cases was 3.1% (95% CI 0.7%–7.2%; I² = 78.8%).

Discussion The pooled proportion of AIS following COVID-19 vaccination is comparable with the prevalence of AIS in the general population and much lower than the AIS prevalence among severe acute respiratory syndrome coronavirus 2–infected patients. TTS is very uncommonly reported in patients with AIS following COVID-19 vaccination.

Background and Objectives Acute arterial ischemic stroke (AIS) has been reported as a rare adverse event following coronavirus disease 2019 (COVID-19) vaccination with messenger RNA (mRNA) or viral vector vaccines. However, data are sparse regarding the risk of postvaccination AIS and its potential association with thrombotic-thrombocytopenia syndrome (TTS).

Methods A systematic review and meta-analysis of randomized controlled clinical trials (RCTs), pharmacovigilance registries, registry-based studies, observational cohorts, and case-series was performed with the aim to calculate the following: (1) the pooled proportion of patients presenting with AIS following COVID-19 vaccination; (2) the prevalence of AIS after mRNA and vector-based vaccination; and (3) the proportion of TTS among postvaccination AIS cases. Patient characteristics were assessed as secondary outcomes.

Results Two RCTs, 3 cohort studies, and 11 registry-based studies comprising 17,481 AIS cases among 782,989,363 COVID-19 vaccinations were included in the meta-analysis. The pooled proportion of AIS following exposure to any COVID-19 vaccine type was 4.7 cases per 100,000 vaccinations (95% CI 2.2–8.1; I² = 99.9%). The pooled proportion of AIS following mRNA vaccination (9.2 cases per 100,000 vaccinations; 95% CI 2.5–19.3; I² = 99.9%) did not differ compared with adenovirus-based vaccination (2.9 cases per 100,000 vaccinations; 95% CI 0.3–7.8; I² = 99.9%). No differences regarding demographics were disclosed between patients with AIS following mRNA-based or vector-based vaccination. The pooled proportion of TTS among postvaccination AIS cases was 3.1% (95% CI 0.7%–7.2%; I² = 78.8%).

Discussion The pooled proportion of AIS following COVID-19 vaccination is comparable with the prevalence of AIS in the general population and much lower than the AIS prevalence among severe acute respiratory syndrome coronavirus 2–infected patients. TTS is very uncommonly reported in patients with AIS following COVID-19 vaccination. source