People with blood type O maybe less vulnerable to Covid-19 and have a reduced likelihood of getting severely ill, according to two studies published. However, experts suggested more research.
The research provides further evidence that blood type may play a role in a person’s susceptibility to infection and their chance of having a severe bout of the disease. The reasons for this link aren’t clear and more research is needed to say what implications, if any, it has for patients.
A Danish study found that there were fewer positive results among those with blood type O.
The findings revealed the most common while peers with blood type A and AB were the most vulnerable. Rates of infection were similar in these three groups.
Researchers in Canada found that among 95 patients critically ill with Covid-19, a higher proportion with blood type A or AB required mechanical ventilation compared with patients with blood group O or B, which was 61%.
The Canadian study also found those with blood type A or AB had a longer stay in the intensive care unit, a median of 13.5 days, compared with those with blood group O or B, who had a median of nine days.
While there are several theories, researchers don’t yet know what mechanism could explain the link between different blood groups and Covid-19.
Mypinder Sekhon, an intensive care physician at Vancouver General Hospital and an author of the Canadian study said it could be explained by people with blood type O having less of a key clotting factor making them less prone to coagulation problems in the blood. Clotting has been a major driver of the severity of Covid-19.
Other possible explanations involve blood group antigens and how they affect the production of infection fighting antibodies. Or it could be linked to genes associated with blood types and their effect on receptors in the immune system.
“It’s a repeated, interesting scientific observation that really warrants further mechanistic work,” he said.
A separate study, published in The New England Journal of Medicine in June, found genetic data in some Covid-19 patients and healthy people suggesting that those with Type A blood had a higher risk of becoming infected, and those with type O blood were at a lower risk.