Thromboembolism after COVID-19 Vaccination: A Systematic Review of Such Events in 286 Patients

Background: Development of vaccines with high efficacy against COVID-19 disease has ushered a new ray of hope in the fight against the pandemic. Thromboembolic events have been reported after administration of vaccines. We aim to systematically review thromboembolic events reported after COVID-19 vaccination. Methods: The available literature was systematically screened for available data on thromboembolic events after COVID-19 vaccination. Data were extracted from selected studies and analyzed for site of thromboembolism as well as other risk factors. All data were pooled to determine cumulative incidence of thromboembolism at various sites after vaccination. Results: A total of 20 studies were selected for the final analysis. The mean age of the population was 48.5 +/- 15.4 years (females - 67.4%). The mean time to event after vaccination was 10.8 +/- 7.2 days. Venous thrombosis (74.8%, n = 214/286) was more common than arterial thrombosis (27.9%, n = 80/286). Cerebral sinus thrombosis was the most common manifestation (28.3%, n = 81/286) of venous thrombosis followed by deep vein thrombosis (19.2%, n = 49/254). Myocardial infarction was common (20.1%, n = 55/274) in patients with arterial thrombosis followed by ischemic stroke (8.02%, n = 22/274). Concurrent thrombosis at multiple sites was noted in 15.4% patients. Majority of patients had thrombocytopenia (49%) and anti-platelet factor 4 antibodies (78.6%). Thromboembolic events were mostly reported after the AstraZeneca vaccine (93.7%). Cerebral sinus thrombosis was the most common among thromboembolic events reported after the AstraZeneca vaccine. Among the reported cases, mortality was noted in 29.9% patients. Conclusions: Thromboembolic events can occur after COVID-19 vaccination, most commonly after the AstraZeneca vaccine. Cerebral sinus thrombosis is the most common manifestation noted in vaccinated individuals.