Thromboembolic Events after COVID-19 Vaccination: An Italian Retrospective Real-World Safety Study

Introduction: Real-world safety studies can provide important evidence on the thromboembolic risk associated with COVID-19 vaccines, considering that millions of people have been already vaccinated against COVID-19. In this study, we aimed to estimate the incidence of thromboembolic events after COVID-19 vaccination and to compare the Oxford-AstraZeneca vaccine with other COVID-19 vaccines. Methods: We conducted a retrospective real-world safety study using data from two different data sources: the Italian Pharmacovigilance database (Rete Nazionale di Farmacovigilanza, RNF) and the Campania Region Health system (Sistema INFOrmativo saNità CampanIA, SINFONIA). Information on COVID-19 vaccinations and thromboembolic events were extracted from the two databases. The reporting rate (RR) and its 95% CI of thromboembolic events for 10,000 doses was calculated for each COVID-19 vaccine. Moreover, the odds of being vaccinated with the Oxford-AstraZeneca vaccine vs. the other COVID-19 vaccines in cases with thromboembolic events vs. controls without thromboembolic events were computed. Results: A total of 12,692,852 vaccine doses were administered in the Campania Region. A total of 641 ICSRs with COVID-19 vaccines and vascular events were retrieved, with 292 thromboembolic events. The higher RRs of thromboembolic events were found with the Oxford-AstraZeneca vaccine (RR: 4.62; 95% CI: 3.50–5.99) and the Janssen vaccine (RR: 3.45; 95% CI: 0.94–8.82). Thromboembolic events were associated with higher odds of exposure to Oxford-AstraZeneca vs. Pfizer-BioNtech (OR: 6.06; 95% CI: 4.22–8.68) and vs. Moderna (OR: 6.46; 95% CI: 4.00–10.80), with no difference vs. Janssen.