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.

Jue Liu, Min Liu, Francesca Futura Bernardi, Annamaria Mascolo, Marina Sarno, Nicolina Capoluongo, Ugo Trama, Rosanna Ruggiero, Liberata Sportiel, Giovanni Maria Fusco, Massimo Bisogno, Enri Coscioni, Anna Iervolino, Pierpaolo Di Micco, Annalisa Capuano, Alessandro Perrella