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Risk of Thrombotic Events With Different COVID-19 Vaccines

Compared with first doses of the mRNA COVID-19 vaccines BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna), first doses of the ChAdOx1-S adenovirus vaccine (Oxford/AstraZeneca) had a 30% increased risk of thrombocytopenia, a multinational analysis shows. Another adenovirus-based vaccine, Ad26.COV2.S (Janssen/Johnson & Johnson), showed a statistical trend toward an increased risk of venous thrombosis with thrombocytopenia. “Although rare, the observed risks after adenovirus-based vaccines should be considered when planning further immunisation campaigns and future vaccine development,” the authors conclude.

The international network cohort study used routinely collected data from France, Germany, the Netherlands, Spain, the U.K., and the U.S. Adults receiving at least 1 dose of a COVID-19 vaccine were included in the determination of incidence risk ratios. The main outcome measure was thrombosis with thrombocytopenia syndrome or venous or arterial thromboembolic events within 28 days after COVID-19 vaccination.

“Comparing ChAdOx1-S with a first dose of BNT162b2 revealed an increased risk of thrombocytopenia (pooled calibrated incidence rate ratio 1.33 (95% confidence interval 1.18 to 1.50) and calibrated incidence rate difference of 1.18 (0.57 to 1.8) per 1000 person years),” the researchers report. “Additionally, a pooled calibrated incidence rate ratio of 2.26 (0.93 to 5.52) for venous thrombosis with thrombocytopenia syndrome was seen with Ad26.COV2.S compared with BNT162b2.”

Source: BMJ