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. 2023 Oct 10;11(10):1575.
doi: 10.3390/vaccines11101575.

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

Francesca Futura Bernardi  1 , Annamaria Mascolo  2   3 , Marina Sarno  4 , Nicolina Capoluongo  4 , Ugo Trama  1 , Rosanna Ruggiero  2   3 , Liberata Sportiello  2   3 , Giovanni Maria Fusco  1 , Massimo Bisogno  5 , Enrico Coscioni  6 , Anna Iervolino  7 , Pierpaolo Di Micco  8 , Annalisa Capuano  2   3 , Alessandro Perrella  4   9
Affiliations

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

Francesca Futura Bernardi et al. Vaccines (Basel). .

Abstract

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). From the start date of the COVID-19 vaccination campaign (27 December 2021) to 27 September 2022, information on COVID-19 vaccinations and thromboembolic events were extracted from the two databases. The reporting rate (RR) and its 95% confidence interval (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, of which 6,509,475 (51.28%) were in females and mostly related to the Pfizer-BioNtech vaccine (65.05%), followed by Moderna (24.31%), Oxford-AstraZeneca (9.71%), Janssen (0.91%), and Novavax (0.02%) vaccines. A total of 641 ICSRs with COVID-19 vaccines and vascular events were retrieved from the RNF for the Campania Region, of which 453 (70.67%) were in females. Most ICSRs reported the Pfizer-BioNtech vaccine (65.05%), followed by Oxford-AstraZeneca (9.71%), Moderna (24.31%), and Janssen (0.91%). A total of 2451 events were reported in the ICSRs (3.8 events for ICSRs), of which 292 were 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 Janssen vaccine (RR: 3.45, 95%CI: 0.94-8.82). Thromboembolic events were associated with a higher likelihood of exposure to the Oxford-AstraZeneca vaccine compared to Pfizer-BioNtech (OR: 6.06; 95%CI: 4.22-8.68) and Moderna vaccines (OR: 6.46; 95%CI: 4.00-10.80).

Conclusion: We observed a higher reporting of thromboembolic events with viral-vector-based vaccines (Oxford-AstraZeneca and Janssen) and an increased likelihood of being exposed to the Oxford-AstraZeneca vaccine compared to the mRNA vaccines (Pfizer-BioNtech and Moderna) among thromboembolic cases.

Keywords: COVID-19; safety; thromboembolic events; vaccination.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Odds ratio (OR) of thromboembolic events for Oxford–AstraZeneca vaccine compared to Pfizer-BioNtech, Moderna, or Janssen vaccines.
See this image and copyright information in PMC

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