ABO Blood Groups and Coronavirus Disease 2019 (COVID-19)

1. Are ABO blood groups associated with the risk of COVID-19? Zhao et al4 compared the ABO blood group distribution in 2173 patients with COVID-19 confirmed by SARS-CoV-2 test from three hospitals in Wuhan and Shenzhen, China, with that in normal people from the corresponding regions. The results were consistent in all three hospitals; the pooled results showed an odds ratio (OR) of COVID-19 for blood group A of 1.21 and for blood group O of 0.67. In the largest hospital sample studied (Jinyintan Hospital), blood group A was also associated with a higher risk of death compared with non-A groups, with an OR of 1.48, and blood group O was associated with a lower risk of death compared with non-O groups, with an OR of 0.66. Zietz & Tatonetti5 studied 1559 individuals in New York with known blood groups who received a SARS-CoV-2 test; about half were positive for the virus. Blood group A were associated with increased odds of testing positive for SARS-CoV-2 (OR 1.34), and blood group O was protective (OR 0.80). These observations could not be explained by known risk factors: age, sex, overweight status, diabetes mellitus, hypertension, pulmonary diseases, and cardiovascular diseases, and the effect of ABO blood group was independent of these risk factors. A meta-analysis of these results together with those of Zhao et al4 confirmed the conclusions, despite the highly significant difference between the two populations in the distribution of blood group gene frequencies: