Background: An association between coronavirus disease 2019 (COVID-19) and ABO blood group has been reported. However, such an association has not been studied in the Japanese population on a large scale. Additionally, little is known about the association between COVID-19 and ABO genotype. Therefore, the present study aimed to investigate the association between COVID-19 and ABO blood group/genotype in a large Japanese population.
Methods: All Japanese patients diagnosed with COVID-19 were recruited through the Japan COVID-19 Task Force between February 2020 and October 2021. We conducted a retrospective cohort study involving 1,790 COVID-19 Japanese patients whose DNA was used for genome-wide association study. We compared the ABO blood group/genotype in healthy population (n = 611, control) and COVID-19 patients, and then analyzed the association between the ABO blood group/genotype and clinical outcomes.
Results: Blood group A was significantly more prevalent (41.6% vs. 36.8%) and group O was significantly less prevalent (26.2% vs. 30.8%) in the COVID-19 group than in the control group. Moreover, genotype OO was significantly less common in the COVID-19 group. Further, blood group AB was identified as an independent risk factor for most severe diseases compared with blood group O [aOR (95% CI) = 1.84 (1.00–3.37)]. Similarly, in ABO genotype analysis, only genotype AB was an independent risk factor for most severe disease compared with genotype OO.
Conclusions: Blood group O is protective, whereas blood group A is associated with the risk of infection. Moreover, blood group AB is associated with the risk of ‘most’ severe disease.