COVID-19: unequal risks according to the blood group

LouiseBoyer Journalist Santépublié le, updated in collaboration with Jacques Le Pendu, research director at INSERM

According to several studies, the blood group O is less likely to be contaminated by the COVVI-19, but also less subject to certain complications due to the severe forms of the virus.

1. Natural antibodies to prevent transmission
2. Efficiency according to the representation of ABO groups in the population
3. Severe forms of COVVID: the group O less at risk of certain complications
4. Insufficient protection
5. Do people in the group be able to be infected?
6. A contradictory study relaunches the debates

Developed in March, the idea that blood groups are affected differently by the COVVI-19 has once again been confirmed.On January 22, researchers from INSERM and the University of Nantes published in Viruses the study "Blood groups A, B, and O and COVID-19: fallacious, anecdotal or significant relationship?"in which they analyze the links between the virus and its impact according to the blood group.

Through the analysis of more than forty studies, researchers from Inserm and the University of Nantes were able to "take stock of these relations which had been reported between the blood groups Abo and theCovid-19, see if it was solid and what could be their meanings "explains Jacques Le Pendu, director of research at Inserm and one of the authors of the study.

People of the Blood Group O would be both better protected in the face of infection, but also, less at risk of developing complications when they have severe forms of the coronavirus.

Two "very distinct" phenomena, insists Jacques Le Pendu, but both in the sense of "a reduced risk for the group O".

Natural antibodies to prevent transmission

"There is indeed a relationship between blood groups and the risk of infection by the Sars VOC -2.There is a consensus around that which emerges "assures the researcher specializing in glycobiology and ABO groups.

When transmitting the virus from one person to another, "the virus uses proteins which it is wrapped, in particular the SPIKE protein, covered with a large layer of sugar, to hide from the immune system".The viral particle carries the abo labels of the original carrier.

Opposite, the Abo antigens of the person "are present on the epithelial barriers, that is to say the cells of the respiratory tree (naso-pharynx, the trachea and the large bronchi), the digestive tube (oral mucosa, small intestine) and even the cells that line the genito-cross tract ".The "blood group" is therefore present on "the entry doors of the pathogens".

Starting from this principle, a theory, demonstrated during the epidemic of the Sras in the early 2000s, but still having to be confirmed for the COVVI-19, assumes that: "Natural anti-dress antibodies, which are essential to define theBlood transfusion rules, would also be to neutralize the virus in the incompatibility situation at the time of the transmission of the virus.If someone in a blood group has transmitted the virus to a person O, their anti-A antibodies could neutralize the virus, "sums up Jacques le Pendu.

Group O people would thus be able to protect themselves from the transmission of the virus by other blood groups.

Efficiency according to the representation of ABO groups in the population

"The risk is variable from one country to another depending on the frequency of blood groups in the population," explains Jacques le Pendu "The effect is not seen in countries where there are a lot of blood groups o, as inSouth America.When you have a balance between people in each blood group, as in South Korea, the risk for O is decreased ".

If the blood groups are fairly represented, the number of incompatible ABO interactions will be more important."The more you have incompatible interactions abo in a population, the more the epidemic should be slowed down".

"In the countries where you have a lot of blood group o, and a bad representation either of the A, or the B or both, this is the case of Peru, then you have an important number of cases and seroprevalence",illustrates the researcher.Despite the application of effective measures in other countries, Peru will lack "this natural protection which decreases the overall risk".

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"If the mechanism is the one we predict, the impact is enormous on the scale of the populations" assures Jacques le hanged.

Severe forms of COVVID: the group O less at risk of certain complications

Unlike some popular ideas, the O group does not prevent the development of serious forms of COVID-19.On the other hand, it could avoid certain complications.

"Once you have developed the serious form, so there is an impact" explains the researcher."People of blood group O have a slightly reduced risk of mortality or recover a little faster".

Certain complications are less frequent in people in the blood group o due to coagulation factors."Groups O have 30% of fewer coagulation factors and are less likely to develop thrombosis or hair micro-thrombosis" begins the Inserm research director, "there are a number of cardio-vascular which has been known for a long time that the risk is associated with the blood groups ABO.And this is what we find in the severe forms of COVID-19, with pulmonary micro-thrombosis ".

Insufficient protection

If the blood group seems to have an impact on the transmission of the virus and the development of complications in severe forms, it cannot serve as a protection.These data make it possible to assess the probabilities of slowing the epidemic and not the lack of risk individually.

"People remain, even if they are from the blood group o, at risk of being infected and that does not change anything to do in terms of respect for barriers' gestures," said Jacques le Pendu.

Do people in the group be able to be infected?

A new study published on March 3 in Blood Advances suggests that people in blood group A have, not only more likely to be infected with the virus but also to develop more severe forms.Research has shown that the protein on the surface of the virus has special affinities with group A and in particular with antigens present on throat cells and lungs.And this, more than for other blood groups.

"If patients are more likely to contract the virus when they are blood group A, they may also be more likely to be infected with more sras-cov-2 virions, which has been associated with more progressionserious disease, "said Sean R.Stowell, who led the research group, at La Vanguardia.

Researchers from the Harvard Medicine School, which cause the study, assure that these results could help research develop substances capable of inhibiting or preventing infection.

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A contradictory study relaunches the debates

Published on Jama Network, doctors' research at the Salt Lake City Cardiology Research Center in the United States seem to contradict the previous results.By analyzing the data of 107,796 people, of which 11,468 were tested positive for the COVVI-19, the researchers confirmed age and sex as risk factors (men and the elderly are more at risk).

However, they could not highlight a correlation between blood group and infection or severe form of coronavirus.A new study which therefore contradicts many others.The contrary results of previous studies on "reduced sample" could be due "to fortuitous variations, publication biases, differences in genetic heritage, geography and the environment, and viral strains" according to the teamfrom Salt Lake City.New research should see the light of day to determine whether or not there is a link between blood groups and the infection or severe forms of COVVI-19.