Controversy around the role of the blood group in Covid-19

Is the blood group a risk factor for Covid-19? Contrary to several studies, American doctors observed that blood types had no influence on the severity of the disease and the risk of becoming infected. The debate is revived.

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The Covid-19 can be a disease that goes unnoticed as much as a fatal disease requiring heavy management and lasting consequences. Doctors quickly wanted to know if there were any risk factors genetics or environmental factors that predict the gravity of Covid-19. Several studies have identified the blood group as being one of them. Indeed, Chinese and American doctors have each observed that there were more people with blood type A admitted to intensive care and that the coronavirus preferentially attaches itself to the cells of these same people. Conversely, blood type O would protect against severe forms of the disease.

But the doctors of theIntermountain Medical Center Heart Institute de Salt Lake City, in the United States, did not come to the same conclusions. For them, the blood group has no positive or negative effect on susceptibility to coronavirus and on the severity of Covid-19. They report their results in a research letter published in Jama Network Open.

Blood group: risk factor or not?

In Salt Lake City, doctors conducted a case-control study using electronic data from patients at their hospital. A total of 107,796 individuals for whom the status of coronavirus infection, blood type, as well as age and sex have been entered in the database. Among them, 11,468 people are positive for the coronavirus; doctors compared the profile of those needing hospitalization or not, and those needing intensive care or not.

As has been observed since the beginning of theepidemic, age is a factor increasing the risk of hospitalization. The average age of people hospitalized is 57 years, against 41.9 years for those who do not need it. Gender is also a factor increasing the risk of disease severity: 61.8% of patients admitted to intensive care are men. But no such link has been observed for blood groups. Among the infected, the proportion of groups O, A, B or AB remains the same for people hospitalized or not, and for those requiring intensive care or not. According to these results, type A does not constitute a risk factor to be infected, hospitalized or admitted to intensive care compared to type O.

Further studies are needed to see more clearly

How can we explain that other researchers have come to the opposite conclusion? Salt Lake City scientists write in their study that “ the small sample sizes and the retrospective and observational nature of many previous studies, in addition to their heterogeneity in associations between ABO groups and the susceptibility and severity of the disease, could be due to accidental variations, publication bias, and differences in genetic background, geography, environment, and viral strains. »They thus consider that blood groups should not be considered as a risk factor potential.

This does not necessarily call into question the observations of the American team on the fact that the coronavirus preferentially binds to the cells of people in group A, but if we consider these results, this is irrelevant.incidence on the infection and severity of Covid-19. As Rome was not built in a day, science, in its progress, sometimes goes backwards. In the case of blood groups and Covid-19, further studies will be needed to arrive at the most likely explanation.

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