Susceptibility to contagion with the Sars-CoV-2 virus can vary according to the blood group: individuals in group O tend to be at lower risk, while the rest are also potentially more exposed to severe clinical conditions.
The findings of two articles, published on Wednesday (14) by the scientific journal Blood Advances, confirm hypotheses presented since last March.
A retrospective study was carried out by the University Hospital of Odense, Denmark, where scientists compared the health records of more than 473,000 individual tests of covid-19 with a control group of 2.2 million, from the general population.
Blood type O was about 13% less likely to test positive for covid-19 than type A, B or AB. These results, however, do not imply greater risk of hospitalization, emphasize the Danish authors.
In another study, from the University of British Columbia, Canada, 95 severe covid-19 patients were hospitalized in Vancouver. Blood groups A and AB were more associated with a risk of severe disease progression, requiring more often artificial respiration, or dialysis for renal failure. In addition, types A and AB tended to require longer ICU stays than O or B blood.
It is not the first time that scientific research has linked susceptibility to respiratory disease and its evolution to blood groups. In March, a study – not submitted to independent review (peer review) – concluded in China that type A blood carriers were more easily infected.
Then, based on medical data from 750,000 individuals, the biotechnology company 23andMe disclosed that type O would be between 9% and 18% more exposed to contracting the new coronavirus.
In June, German and Norwegian researchers released results after following 1,610 critically ill patients from covid-19 epicenters in Spain and Italy. They examined certain stretches of DNA where frequent genetic mutations occur, and the characteristics observed were compared with blood samples from 2,205 healthy individuals.
Those belonging to blood group A showed a 45% higher risk of a serious course, with twice the chance of needing oxygen or artificial respiration. In contrast, O blood would have a kind of protective effect, implying 35% less risk.
Some experts suggest that the association may be due to the different antibodies produced by the different blood types, or how they can affect clotting ability. On the other hand, other research – such as that carried out by Harvard Medical Schoolin Massachusetts, and at Columbia Presbyterian Hospital, from New York – found no correlation.
Although the Harvard study showed a greater likelihood between types B and AB, positive Rh factor, of testing positive for coronavirus, it was also found that even symptomatic patients in blood group O were less likely to show positive results on tests .
“These results need to be explored further, to determine whether there is something inherent in these blood types, potentially capable of providing protection or reducing risk for individuals,” said the study’s lead author, Anahita Dua.