A growing number of research show that blood type may play a vital role when it comes to getting infected with the deadly coronavirus. Two new studies suggest people with blood type O may be at a lower risk of contacting Covid-19 and have a reduced likelihood of getting severely ill.
It's not yet clear what's causing the statistical connection found in two studies released Wednesday, one in Denmark and one in Canada, and experts say more research is required. The two studies were published in the journal Blood Advances, a publication of the American Society of Hematology and gives and insight into the role of different blood groups while becoming infected with the virus.
Blood Type O Safest?
The two studies provide further evidence that blood type or blood group may play a major role in a person's susceptibility to infection and their chance of having a severe bout of the disease. The first research done in Denmark on 473,654 people who were tested for Covid-19 between February and July found only 7,422 tests with blood type O came back positive.
However, even though among a group of 2.2 million people who were not tested for Covid-19, the blood type made up 41.7 percent of the population. By contrast, 44.4 percent of type A tested positive, while in the wider Danish population that blood type makes up 42.4%.
"Blood group O is significantly associated with reduced susceptibility to SARS-CoV-2 infection," the study authors wrote, meaning that people with type O blood seemed 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 type A or AB — 84 percent — required mechanical ventilation compared with patients with blood group O or B, which was 61 percent.
The study also found that those with type A or AB blood had a median stay in the intensive care unit of 13.5 days, compared to 9 days for those with type O or B, the study found.
More Research Needed
However, in both the studies scientists said that more research was required. "We do not know whether this is some kind of protection of group O, or whether it's some kind of vulnerability in the other blood groups," Dr. Torben Barington, the senior author of the Danish study said.
Most humans fall into one of four blood groups: A, B, AB or O. In the United States, the most common blood groups are O and A. However, still the United States has the highest number of infections and deaths from Covid-19 till date. While there are several theories, researchers don't yet know what mechanism could explain the link between different blood groups and Covid-19.
The findings of the two new studies provide "more converging evidence that blood type may play a role in a person's susceptibility to Covid infection and their chance of having a severe bout of Covid-19," said Dr. Amesh Adalja, senior scholar at the Johns Hopkins University Center for Health Security in Baltimore, who was not involved in either of the studies.