Role of the AB0 blood group in COVID-19 infection and complications: A population-based study

•Aim: Evaluate the role of ABO group on the risk of SARS-CoV-2 infection and related complications.•Design: Population-based cohort including 87,090 patients from the Northern Spain.•Findings (I): 6% absolute risk reduction of SARS-CoV-2 infection in O blood group.•Findings (II) 9% absolute risk increase in A blood group Since the beginning of the COVID-19 pandemic, the ABO blood group has been described as a possible biological marker of susceptibility for the disease. This study evaluates the role of ABO group on the risk of SARS-CoV-2 infection and related complications in a population-based cohort including 87,090 subjects from the Navarre population (Northern Spain) with no history of SARS-CoV-2 infection and with known ABO blood group, after one year of the pandemic (May 2020 – May 2021). The risk of infection, hospitalization, Intensive Care Unit (ICU) admission and death was analyzed using multivariate logistic regression, adjusting for possible confounding variables. A lower risk of infection was observed in group 0 vs non-0 groups [OR 0.94 (95 %CI 0.90−0.99)], a higher risk of infection in group A vs non-A groups [OR 1.09 (95 %CI 1.04−1.15)] and a higher risk of infection in group A vs group 0 [OR 1.08 (95CI 1.03−1.14)] (when the 4 groups are analyzed separately). No association was observed between blood groups and hospitalization, ICU admission, or death in SARS-CoV-2 infected subjects. Regarding the risk of SARS-CoV-2 infection, we observed a protective role of group O and a greater risk in the A group.