The researchers found that the adjusted relative risk for SARS-CoV-2 infection was 0.88 for blood group O versus the A, AB, and B blood groups together. Rh− blood type was associated with a reduced risk for SARS-CoV-2 infection (adjusted relative risk, 0.79), especially for those who were O-negative (adjusted relative risk, 0.74). The risk for severe COVID-19 illness or death was lower in association with the type O blood group versus all others (adjusted relative risk, 0.87) and for Rh− versus Rh-positive (adjusted relative risk, 0.82).
