Anti-A and SARS-CoV-2: an intriguing association

Vox Sang. 2021 May;116(5):557-563. doi: 10.1111/vox.13044. Epub 2021 Mar 2.


Background: Blood groups and anti-A isohemagglutinin may be involved in susceptibility to SARS-CoV-2 infection.

Materials and methods: We retrospectively studied 268 COVID-19 convalescent plasma donors and 162 COVID-19 inpatients (total 430 subjects, confirmed by RT-PCR) and 2,212 healthy volunteer first-time blood donors as a control group. These were further divided into two groups: those with anti-A (blood types O and B) and those without it (types A and AB). Titres of nucleoproteins, and neutralizing SARS-CoV-2 antibody were measured in the convalescent plasma donors and inpatients. Multivariate logistic regression and non-parametric tests were applied.

Results: Persons having types O or B showed less infection prevalence than those of types A or AB (OR = 0·62, 95% CI 0·50-0·78; P < 0·001), but there was no difference when COVID-19 inpatients were analysed. Immunoglobulins M, G and A were lower in COVID-19 subjects of types O or B group than those of A or AB (0·16 vs. 0·19; P = 0·03, 2·11 vs. 2·55; P = 0·02, 0·23 vs. 0·32; P = 0·03, respectively).

Conclusion: In this retrospective cohort, COVID-19 individuals were less likely to belong to blood types O and B, and also had lower SARS-CoV-2 antibody titres than A and AB individuals. COVID-19 severity did not associate with the blood groups.

Keywords: ABO groups; SARS-CoV-2; anti-A.

MeSH terms

  • ABO Blood-Group System / blood*
  • Adult
  • Antibodies, Neutralizing / blood
  • Antibodies, Neutralizing / immunology
  • Antibodies, Viral / blood*
  • Antibodies, Viral / immunology
  • COVID-19 / blood*
  • COVID-19 / immunology
  • COVID-19 / therapy*
  • COVID-19 Serotherapy
  • Hemagglutinins / immunology
  • Humans
  • Immunization, Passive
  • Male
  • Middle Aged
  • SARS-CoV-2 / immunology


  • ABO Blood-Group System
  • Antibodies, Neutralizing
  • Antibodies, Viral
  • Hemagglutinins