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A new study confirms what scientists have constantly suspected during the Covid-19 epidemic: not all blood groups are equal in the face of the virus. There is a more vulnerable blood type… and one that is more resistant.

Since the start of the Covid-1 pandemic, researchers’ work suggests that people with blood type A seem to be more vulnerable to infection, while those with blood type O seem to be a little less susceptible. But no mechanism seemed to explain this apparent imbalance.

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According to a new study from the American Society of Hematology, published in the journal Blood, “a part of the SARS-CoV-2 spike protein that is essential for allowing the virus to invade cells displays an affinity for blood group A cells, and the virus in turn also shows a preferential ability to infect blood group A cells“.

“IResearch shows that people with blood type A are 20% more likely to become infected after exposure to SARS-CoV-2 compared to those with blood type O. But people with blood type O can still get the virus and pass it on to others,” says Dr Sean Stowell, of the Harvard Medical School, lead author of the study.

Blood group 0+ or ​​0 -: what protects them?

In 2021, a consensus seemed to emerge from a growing number of studies: people with blood group 0 seemed to be more resistant to covid-19. The Inserm researchers saw two reasons for this: “First, natural anti-A and anti-B antibodies could be partially protective against SARS-CoV-2 virions. Second, O individuals have blood that clots less , so they are less prone to thrombosis and vascular dysfunction which are complications of covid-19” they point out in the journal Viruses.

Conversely, another study published in the journal Blood advance, indicated that covid-19 seems to cling more easily to cells in the airways of people with blood group A, which would explain why, throughout the pandemic , a larger number of people with blood group A were hospitalized for severe forms of Covid-19.

Laboratory experiments for this study revealed that a part of the coronavirus called the “receptor binding domain” (RBD), which binds to cells to trigger infection, also latches on to type A blood antigens. These antigens are present in the respiratory cells, which would explain why the coronavirus enters and infects them more easily.

A sensitivity pointed out by researchers as early as March 2020

As early as March 2020, Chinese researchers from the University of Shenzhen noted that “people with blood group A have a significantly higher risk of being affected by the Covid-19 coronavirus, while people with blood type O have a lower riskTheir study, involving 2,173 individuals infected with the virus and hospitalized in 3 hospitals in the cities of Wuhan and Shenzhen, was published in the medical journal MedRxiv.

Two studies, one Danish and the other Canadian, published in the journal blood advances, confirmed these findings 7 months later. “It is increasingly recognized that blood groups A, B and O influence susceptibility to certain viruses” underline the Danish researchers. They studied the blood type of 473,654 people tested for Covid-19. In this cohort, 7422 people were positive for SARS-CoV-2 and 466,232 were negative. Among Covid-positive people, “far fewer individuals of group O were found, conversely, more individuals A, B and AB were noted” underline the researchers.

Canadian scientists, for their part, have examined 95 patients with severe Covid-19 and admitted to intensive care at Vancouver Hospital. They found that a higher proportion of patients with blood groups A or AB required mechanical ventilation or continuous renal replacement therapy and that their stay in intensive care was longer compared to patients with blood groups O or B. .

Blood group O: more antibodies

How to explain this difference? A French study published in 2003 had already shown that certain blood groups were more likely to contract the SARS coronavirus. The reason ? People with blood type O naturally have “anti-A” and “anti-B” antibodies – which is why you cannot transfuse AB blood into someone with type O. Therefore, a virus emitted by a person from group A, AB or B will be more easily destroyed by a person from group O. Conversely, people from group A only have “anti-B” antibodies: their “antivirus protection” is therefore less sophisticated than group O people.

I am group 0, am I protected ? People in group 0 (about 42% of the French population) certainly have more antibodies, but it does not offer total immunity to the virus. We must therefore continue to apply barrier gestures.


  • Modeling suggests ABO histo-incompatibility may substantially reduce SARS-CoV-2 transmissionScience Direct, January 2022
  • ABO Blood Types and COVID-19: Spurious, Anecdotal, or Truly Important Relationships? A Reasoned Review of Available DataJanuary 2021, Viruses
  • The SARS-CoV-2 receptor-binding domain preferentially recognizes blood group AMarch 2021, Blood Advance
  • Association of Sociodemographic Factors and Blood Group Type With Risk of COVID-19 in a US PopulationJama Network Open, April 5, 2021

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