Covid-19: unequal risks depending on blood group

According to several studies, blood group O is less at risk of being contaminated by covid-19, but also less subject to certain complications due to severe forms of the virus.

Developed in March 2020, the idea that blood groups would be affected differently by covid-19 has once again been confirmed. People with blood group O are both better protected against infection, but also less at risk of developing complications when they suffer from severe forms of the coronavirus. Two phenomena “very distinct”, insists Dr Alhassane Kamissoko, specialist in glycobiology at Donka University Hospital, but both in the sense “of a reduced risk for group O”.

Natural antibodies to prevent transmission

“There is indeed a relationship between blood groups and the risk of infection with covid-19. There is a consensus around what is emerging,” assures the glycobiology specialist.

When the virus is transmitted from one person to another, “the virus uses proteins from which it is developed, in particular the Spike protein, covered with a large layer of sugar, to hide from the immune system”, explains Dr Alhassane. The viral particle carries ABO labels from the original carrier.

Opposite, the person's ABO antigens, “are present on the epithelial barriers, that is to say the cells of the respiratory tree (nasal-pharynx, trachea and large bronchi), the digestive tract (oral mucosa, small intestine) and even the cells which line the genitourinary tract, the blood group is therefore present on the entry portals of pathogens”, specifies Dr Kamissoko.

The year 2000 theory confirms that of 2019

Based on this principle, a theory, demonstrated during the SARS epidemic of the early 2000s, but still to be confirmed for covid-19, assumes that:“Natural anti-ABO antibodies, which are essential to define the rules of blood transfusion, would also be essential to neutralize the virus in the situation of incompatibility at the time of virus transmission. If someone with blood type A transmits the virus to someone O, their anti-A antibodies could neutralize the virus., summarizes Dr Alhassane Kamissoko.

Group O can protect itself from transmission from other groups

People with group O would thus be able to protect themselves from transmission by other blood groups. “The risk varies from one country to another depending on the frequency of blood groups in the population”, explains Alhassane Kamissoko.

If blood groups are fairly represented, the number of ABO incompatible interactions will be greater.“The more ABO incompatible interactions you have in a population, the more the epidemic should be, at least, slowed down,” says Dr Kamissoko

“In countries where you have an awful lot of O blood type, and poor representation of either A or B or both; then you have significant case numbers and seroprevalence.”, illustrates Dr Alhassane Kamissoko.

Studies that have not given all the answers

Through the analysis of more than forty studies, researchers from Inserm and the University of Nantes were able to take stock of these relationships that had been reported between ABO blood groups and covid-19, to see if they were solid and what their meanings could be.

Amadou Dari DIALLO