People with blood type O, who are less at risk of...

A growing body of research shows that blood type can play an important role in infection with the deadly coronavirus. Two new studies suggest that people with blood type O have a lower risk of coming into contact with Covid-19 and a lower chance of getting seriously ill.

It is not yet clear what causes the statistical association found in two studies published Wednesday, one in Denmark and one in Canada. Experts say more research is needed. The two studies were published in the journal Blood advances, an American Society of Hematology publication that provides insight into the role of different blood types in infection with the virus.

Blood group O safest?

The two studies provide further evidence that blood type or blood type can play an important role in a person’s susceptibility to infection and their likelihood of having a severe attack of the disease. The first study carried out in Denmark on 473,654 people who were tested for Covid-19 between February and July found that only 7,422 tests with blood type O were positive.

Although among a group of 2.2 million people who had not been tested for Covid-19, the blood type made up 41.7 percent of the population. In contrast, 44.4 percent of type A tested positive, while in the wider Danish population, this blood type accounts for 42.4%.

“Blood type O is significantly linked to a reduced susceptibility to SARS-CoV-2 infections,” the study authors wrote, which means that people with type O blood appear to be less likely to become infected.

The other study conducted in Canada shows similar results. Of the 95 patients critically ill with Covid-19, a higher proportion with blood group A or AB (84 percent) required mechanical ventilation compared to patients with blood group O or B (61 percent).

The study also found that those with type A or AB blood had a mean ICU stay of 13.5 days, compared with 9 days for those with type O or B, the study found.

More research needed

However, in both studies, the scientists said more research was needed. “We don’t know if this is some kind of protection in group O or if it is some kind of vulnerability in the other blood groups,” said Dr. Torben Barington, the lead author of the Danish study.

Most people fall into one of four blood types: A, B, AB, or O. In the United States, the most common blood types are O and A. However, the United States still has the highest number of infections and deaths from Covid-19. 19 to date. Although there are several theories, researchers do not yet know what mechanism could explain the connection between different blood types and Covid-19.

The results of the two new studies provide “more convergent evidence that blood type plays a role in a person’s susceptibility to Covid infection and their likelihood of a severe attack of Covid-19,” said Dr. Amesh Adalja, senior scientist at the Johns Hopkins University Center for Health Security in Baltimore, who was not involved in any of the studies.