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Study of ABO and Rh Blood Groups and SARS-CoV-2 Infection
Quick Takes
- The O and Rh− blood groups may be associated with a slightly lower risk for SARS-CoV-2 infection.
- There was no difference in risk of severe illness or death attributable to blood group or Rh positivity in the subgroup of individuals who tested positive for SARS-CoV-2.
- Overall, the magnitude of attributable risk is low, and does not warrant changes in policies or clinical management in patients according to blood group.
Study Questions:
Are ABO and rhesus (Rh) blood groups associated with risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and severe coronavirus disease 2019 (COVID-19)?
Methods:
In this population-based cohort study, the authors queried various national databases in Ontario including the Ontario Health Insurance Plan claims database and the Ministry of Health’s Registered Persons Database to identify all individuals who had ABO blood group assessed between January 2007 and December 2019, and those who had SARS-CoV-2 viral RNA polymerase chain reaction (PCR) testing between January 15–June 30, 2020. The main study outcome was SARS-CoV-2 infection. A second outcome was a composite of severe COVID-19 illness or death up to 14 days after the positive SARS-CoV-2 PCR test. Outcomes were compared across ABO blood group and Rh positivity and stratified by age using 70 as a cut-off.
Results:
A total of 225,556 persons (mean age 54 years, 29% men) with known ABO blood group and SARS-CoV-2 testing were included in the analysis. Of these, 36.3% had blood type A, 4.5% had type AB, 14.9% had type B, and 44.3% had type O. The lowest unadjusted probability of SARS-CoV-2 infection was among the O− blood group (2.1%; 95% confidence interval [CI], 1.8%-2.3%), and the highest was in the B+ blood group (4.2%; 95% CI, 4.0%-4.5%). The adjusted absolute risk difference compared to type A was 4.6% (95% CI, 0.9%-8.4%) for AB, 6.3% (95% CI, 0.9%-8.4%) for B, and -1.5% (95% CI, -3.0% to 0.2%) for O. Rh− status was associated with a lower risk of infection (-6.8%; 95% CI, -8.9% to -4.7%). The effect was more pronounced for those aged <70 years.
There were 1,328 cases of COVID-19 with severe illness or death. In an analysis restricted to those who tested positive for SARS-CoV-2, there was no observed association between blood group and risk of severe illness or death. When including patients who tested negative, there was a higher adjusted absolute risk for blood group B (+1.2%; 95% CI, 0.2%-2.2%) relative to A, as well as those who were Rh+ (+1.1%; 95% CI, 0.2%-2.0%). O had a slightly decreased risk compared to all others (-0.8%; 95% CI, -1.4% to -0.2%).
Conclusions:
The O and Rh− blood groups may be associated with a slightly lower risk for SARS-CoV-2 infection.
Perspective:
This population-based study provides additional supportive evidence of an association between blood group and Rh positivity with risk of SARS-CoV-2 infection. The cohort included <30% men, conferring a high risk of selection bias to the findings. The absolute increased risk of SARS-CoV-2 infection afforded by the non-O blood groups are generally <5%, and no increase in the risk of severe illness or death was noted in the subgroup who tested positive for SARS-CoV-2. The pathophysiologic mechanisms that underlie these differences are unknown, but hypothesized to be due to modulation of sialic acid-containing receptors induced by ABO antigens on host cells impacting viral entry. Overall, the magnitude of attributable risk is low, and does not warrant changes in policies or clinical management in patients according to blood group.
Clinical Topics: COVID-19 Hub, Prevention
Keywords: ABO Blood-Group System, Coronavirus, COVID-19, Diagnostic Tests, Routine, N-Acetylneuraminic Acid, Primary Prevention, Reverse Transcriptase Polymerase Chain Reaction, Rh-Hr Blood-Group System, Risk Assessment, RNA, Viral, severe acute respiratory syndrome coronavirus 2
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