Blood group and Covid: who would have immunity?

[Mis à jour le 8 mars 2022 à 11h28] Since the beginning of the Covid pandemic, several studies have highlighted a link between blood group and the risk of being sick with Covid and develop a severe form. According to the researchers (the first study to have highlighted this link was carried out by Chinese scientists from the University of Shenzhen in March 2020), certain blood groups could be “protected” and others on the contrary more at risk of Covid . A total of forty studies have shown the link between blood type and immunity to Covid-19. O+, O-, A, AB, B… Who is most at risk of being positive for Covid-19? On the contrary, who could be immunized? How do you explain the relationship between blood type and disease risk? Knowledge to date.

What are the blood proteins that “protect” from Covid?

In a study published on March 3, 2022 in Plos Genetics, researchers have analyzed over 3,000 blood proteins and their link with the development of Covid. During their research, they observed that 5 of them were associated with an increased risk of Covid infection and a – protein ABO – was associated with increased hospitalization and need for respiratory assistance. Conversely, 8 proteins – mainly playing a role in cell adhesion – were causally associated with a reduced risk of hospitalization and respiratory assistance.

Which blood group is the most at risk of Covid according to studies?

According to studies, group O would be the most protected against Covid infection. “You have less serious forms if you have a group O, because group O is less prone to thrombosesand we know that this is one of the forms of aggravation of the Covid”commented Dr. Alain Ducardonnet, cardiologist in Paris on the set of the Morning of BFMTV on February 4, 2022.

► In March 2020, a first statistic study published on the scientific pre-publication site “MedRxiv” and conducted by Chinese researchers from the University of Shenzhen had shown that:

• Group O people would have 33% less risk of being contaminated by the new coronavirus compared to people in groups B and AB.
• Group A people would have an over-risk of 20% to be infected with the new coronavirus compared to people in groups B and AB.
• These two hypotheses seem valid regardless of the sex or age of the individual studied. “At the individual level, this does not change the need to protect oneself, but at the population level, it is interesting“, estimates Jacques le Pendu, immunologist and research director of Inserm on Ouest France.

► In June 2020, a studypublished in The New England Journal of Medicine, conducted on 1,980 people with Covid-19, reached the same results: a higher risk of contracting Covid-19 in blood group A compared to other blood groups and a protective effect in blood group O compared to other blood groups.

► January 22, 2021, a french study conducted by researchers from INSERM and the University of Nantes, led by immunologist Jacques Le Pendu and published in the journal Viruses, shows that blood group O seemed “protective compared to non-O types”. “Despite discrepancies between studies, a general consensus emerged that blood type O appears to be associated with a lower risk of COVID-19, while non-O blood types appear to be detrimental.“, indicate the authors of the study. Two major hypotheses can explain these results: Firstnatural anti-A and anti-B antibodies may be partially protective against virions (infectious particles of a virus made up of nucleic acid and protein) of SARS-CoV-2 carrying blood group antigens from non-O individuals. Secondlyindividuals O are less prone to thrombosis and vascular dysfunction than non-O individuals and may therefore be less exposed in cases of severe lung dysfunction.

“A general consensus has emerged that blood type O appears to be associated with a lower risk of COVID-19“

► Of them other scientific studies whose results were published on October 14 in Blood Advances magazine from the American Society of Hematology provide details on the link between blood type and severity of coronavirus infection.

• The first study of 473,000 people who tested positive for Covid-19 showed that Danish patients with COVID-19 with type O or B blood spent less time in an intensive care unit than their type A or type counterparts. AB. They also needed less mechanical breathing and dialysis because they suffered less kidney failure.
• The second study carried out on 95 patients severely affected by Covid-19 in a hospital in Vancouver (Canada) between February and April 2020 also showed that patients with type O or B blood passed on average 4.5 fewer days in the intensive care unit than those with type A or AB blood who stayed an average of 13.5 days in an intensive care unit.

► February 4, 2021a Spanish study, conducted by researchers from the IVI group in Barcelona (specialized in fertility treatment) and presented at the last edition of the American Society for Reproductive Medicine Congressshows that, based on data collected from 6,140 patients with Covid-19 between May and June 2020, people from blood group O+ seem the best protected against the disease. “For the analyzed sample, the positivity rate does not vary significantly with age or sex. However, people who are Rh negative have been found to have a slightly higher risk of infection than those who are Rh positive.“, says Dr. André Guérin, gynecologist at the IVI clinic in Barcelona. In other words, group people O+ would have less risk to test positive for Covid-19, but they could still contract the virus and eventually develop a severe form. These people are in no way immune and must take precautions against the virus, especially with the emergence of variants.

What is the influence of blood group on antibodies?

The composition of blood is the same for everyone. On the other hand, the antigens present on the surface of blood cells (red and white blood cells, etc.) differ from one person to another. People are divided into 4 blood groups: O, A, AB and B. “Depending on whether they have the A antigen (and anti-B antibodies), the B antigen (and anti-A antibodies), both or neither, people are therefore divided into blood group A, B, AB or O.”, specifies Inserm on its website.

Depending on our blood group, our blood develops different antibodies.

“For me, the relationship between blood group and the risk of contracting the virus is now established. If the causal link has not yet been demonstrated, all these studies converge in their results on the fact that blood groups O are less at risk than the others.“, indicates Jacques le Pendu, immunologist at the Nantes-Angers Cancer Research Center, duringan interview with Marianne. But this percentageis not important enough not to take precautions”, he insists. “This [résultat] is not surprising. We found the same thing during a 2003 study on the SARS virus epidemic (coronavirus very close to Covid-19, editor’s note)“, specifies Jacques Le Pendu, this time, to France Inter. In 2008, a French study published in Glycobiology in which Jacques Le Pendu had participated proposed a beginning of explanation. Depending on our blood group, our blood develops different antibodies. The plasma that makes up the blood contains anti-A and anti-B antibodies in people with group O, all rhesus combined, which would represent a potential double defense against a virus, such as Covid-19 for example. In contrast, the plasma of people with group A contains only one type of antibody (anti-B), which would constitute a single potential defense against a virus.

What are the limitations of these studies?

Of course, the results of these four studies should be taken with a grain of salt. In other words, not everyone in group A will necessarily be infected with the coronavirus. And conversely, people in group O are not immune to Covid-19 either. “There is only a small rate of protection or risk of infection, which clearly indicates that several other factors are involved in this disease. Further research is therefore needed to establish this link.“, comments Dr. Sakthivel Vaiyapuri, Associate Professor of Pharmacology-cardiovascular disease and poisonous substances at the University of Reading in England. These results could therefore constitute an additional avenue of research for the development of a treatment or a vaccine against the coronavirus. In all cases, regardless of their blood group, only the fact of respecting barrier gestures makes it possible to minimize the risk of infection.

The blood test, prescribed by your attending physician, is the simplest and most common method to find out your blood type. After your appointment at a laboratory or medical center, you will be given a blood group card which will indicate whether you are A, B, AB or O and Rh (+ or -). Note that you can also find out your blood group when donating blood.

What is the rarest and most common blood type?

Sources

– Relationship between the ABO Blood Group and the COVID-19 Susceptibility, Medrxiv, 16 mats 2020. To achieve this result, the research team analyzed the state of health and the blood group of 2,173 people infected with Covid -19, from three hospitals in Wuhan and Shenzhen, of which 206 had died from novel coronavirus infection. They then compared them to the health status and blood type of 3,694 Wuhan residents not infected with the coronavirus.

– Inhibition of the interaction between the SARS-CoV Spike protein and its cellular receptor by anti-histo-blood group antibodies, Patrice Guillon, December 2008, Glycobiology.

– Reduced prevalence of SARS-CoV-2 infection in ABO blood group O, October 14, 2020, Blood Advances.