Objectives: To determine whether blood group influences development of cerebral venous thrombosis (CVT) after administration of the coronavirus disease 2019 (COVID-19) AstraZeneca ChAdOx1-S vaccine.
Design: A case-control study. Univariate and multivariate logistic regression was used to determine the association between blood type and COVID-19 vaccination status.
Setting: Vaccinated and unvaccinated patients recruited from the international Bio-Repository to Establish the Aetiology of Sinovenous Thrombosis study and the Cerebral Venous Sinus Thrombosis With Thrombocytopenia Syndrome Study Group.
Participants: All patients were of European descent and age and sex matched. Cases (n = 82) were patients ≥18 years old who suffered a CVT within 28 days of a first dose of ChAdOx1-S vaccine. Controls (n = 441) were unvaccinated CVT patients ≥18 years old. All patients were of European descent.
Main outcome measures: Frequency of blood type and ABO allele distribution by vaccination status.
Results: Blood group O was found to be more prevalent among CVT patients with vaccine-induced thrombotic thrombocytopenia (VITT-CVT) after ChAdOx1-S vaccination compared with unvaccinated CVT cases (43% vs. 17%, respectively, p < 0.001). Blood group A was less prevalent, though still high, in the vaccinated group compared with the unvaccinated group (47% vs. 71%, respectively, p < 0.001). No significant differences were observed in the VITT-CVT non-ChAdOx1-S vaccine group and unvaccinated pre-COVID-19 CVT group for blood group.
Conclusions: Blood group O is more prevalent among patients with VITT-CVT after ChAdOx1-S vaccination compared with unvaccinated cases, independent of well-established CVT risk factors. A larger dataset may be able to determine whether those of blood groups B and/or AB may be safely vaccinated with the low cost, readily available and easily transported ChAdOx1-S rather than adopting a complete ban.
Keywords: ChAdOx1-S COVID-19 vaccine; Oxford-AstraZeneca; blood group; cerebral venous thrombosis.