The relationship between blood groups and risk of infection with SARS-CoV-2 or development of severe outcomes: A review.

The outbreak of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is considered a global catastrophe that has overwhelmed health care systems. Since initiation of the pandemic, identification of characteristics that might influence risk of infection and poor disease outcomes have been of paramount interest. Blood group phenotypes are genetically inherited characteristics whose association with certain infectious diseases have long been debated. The aim of this review is to identify whether a certain type of blood group may influence an individual's susceptibility to SARS-CoV-2 infection and developing severe outcomes. Our review shows that blood group O protects individuals against SARS-CoV-2, whereas blood group A predisposes them to being infected. Although the association between blood groups and outcomes of COVID-19 is not consistent, it is speculated that non-O blood group carriers with COVID-19 are at higher risk of developing severe outcomes in comparison to O blood group. The interaction between blood groups and SARS-CoV-2 infection is hypothesized to be as result of natural antibodies against blood group antigens that may act as a part of innate immune response to neutralize viral particles. Alternatively, blood group antigens could serve as additional receptors for the virus and individuals who are capable of expressing these antigens on epithelial cells, which are known as secretors, would then have a high propensity to be affected by SARS-CoV-2.