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Blood system ABO antigens as risk factor for severity of SARS-CoV-2 infection.

Introduction
Whether there is an influence of the ABO blood system on SARS-CoV-2 infection is unknown.


Objective
To analyze if there is an association between the ABO system antigens and susceptibility to and severity of SARS-CoV-2 infection.


Material and methods
The frequency of ABO system antigens was compared in 73 confirmed cases of SARS-CoV-2 infection and 52 clinically healthy donors. Infection severity was assessed by comparing the frequency of antigens by disease severity and mortality.


Results
The risk of suffering from SARS-CoV-2 infection increases in subjects with A vs. non-A antigen (OR = 1.45; 95 % CI: 1.061-1.921). Blood phenotype O reduces the risk of SARS-CoV-2 infection (OR = 0.686; 95 % CI: 0.522-0.903). No differences were found regarding disease severity. In critically ill patients, the risk of mortality increased in subjects with A vs. non-A antigen (OR = 3.34; 95 % CI: 1.417-8.159).


Conclusion
Blood group A is a risk factor for SARS-CoV-2 infection, but not for disease severity, although in critically ill patients it is a risk factor for mortality.