• Gie Ken-Dror, Pankaj Sharma, and international Bio-Repository to Establish the Aetiology of Sinovenous Thrombosis (BEAST) collaborators and Cerebral Venous Sinus Thrombosis With Thrombocytopenia Syndrome Study Group.
• Institute of Cardiovascular Research Royal Holloway, University of London (ICR2UL), London TW20 0EX, UK.
• J R Soc Med. 2024 Feb 1; 117 (2): 697669-76.

ObjectivesTo determine whether blood group influences development of cerebral venous thrombosis (CVT) after administration of the coronavirus disease 2019 (COVID-19) AstraZeneca ChAdOx1-S vaccine.DesignA case-control study. Univariate and multivariate logistic regression was used to determine the association between blood type and COVID-19 vaccination status.SettingVaccinated 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.ParticipantsAll 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 MeasuresFrequency of blood type and ABO allele distribution by vaccination status.ResultsBlood 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.ConclusionsBlood 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.

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