Blood Type Linked to Risk of COVID-19 Infection Severity

Identification of risk factors for contracting and developing serious illness following infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is of paramount interest. Development of COVID-19 is associated with age, sex, and comorbidities, such as cardiovascular diseases, although severe disease is not limited to these risk groups.

Blood group A and B glycosyltransferases also affect glycosylation in a large number of cell types, including epithelial cells in the respiratory tract and shed viral particles. A, B, and AB individuals are also at increased risk for thrombosis and cardiovascular diseases, which are important comorbidities among hospitalized COVID-19 patients, possibly mediated by glycosylation of proteins involved in hemostasis.

Clinical Immunologists at the Odense University Hospital (Odense, Denmark) and their colleagues analyzed data in a retrospective cohort study, of over 840,000 individuals in Denmark who underwent testing by polymerase chain reaction for SARS-CoV-2 between February 27 and July 30, 2020. Most of those tested (56%) had available ABO and RhD blood group information. The team also used ABO and RhD data of 2,204,742 individuals not tested for SARS-CoV-2 as a reference. This corresponded to approximately 38% of the entire Danish population.

The scientists reported that of the 473,654 tested individuals who had a known blood group, 7,422 were positive for SARS-CoV-2 and 466,232 were negative. The positive and negative groups had similar proportions of men (32.9% versus 32%) and similar median ages (52 years versus 50 years). Among patients with SARS-CoV-2, considerably fewer (38.4%) had blood type O than other tested blood types. When excluding blood type O, they observed no significant differences among patients with blood types A, B and AB. They also observed no difference in the RhD group between positive cases and the reference population. The investigators reported relative risk (RR) for contracting SARS-CoV-2 of 0.87 for blood type O, 1.09 for blood type A, 1.06 for blood type B and 1.15 for blood type AB.

Torben Barington, MD, a Professor of Medicine and the senior author of the study, said, “ABO blood groups are increasingly recognized to influence susceptibility to certain viruses, including SARS-CoV-1 and norovirus. A, B and AB individuals are also at increased risk for thrombosis and cardiovascular diseases, which are important comorbidities among hospitalized COVID-19 patients, possibly mediated by glycosylation of proteins involved in hemostasis.” The study was originally published on October 14, 2020 in the journal Blood Advances.

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