Two studies published Wednesday suggest that people with blood type O may have a reduced chance of catching the coronavirus and may have less severe infections thereafter. The reasons why this may be so is still unknown:
A Danish study found that among 7,422 people who tested positive for Covid-19, only 38.4% were blood type O — even though, among a group of 2.2 million people who were not tested, that blood type made up 41.7% of the population.
By contrast, 44.4% of group A tested positive, while in the wider Danish population that blood type makes up 42.4%…
They found that blood group wasn’t a risk factor for hospitalization or death from Covid-19.
Dr. Roy Silverstein from the Medical College of Wisconsin told NBC News the difference isn’t that large:
“The study suggests if you have type O, you have a slightly lower risk,” Dr. Roy Silverstein, chair of medicine at the Medical College of Wisconsin, said. “But it’s a small decrease,” he said, adding that blood type does not equate to zero percent risk. Silverstein, who is also a former president of the American Society of Hematology, was not involved with the new studies.
What’s more, Silverstein pointed out, the new research will not alter how doctors treat Covid-19 patients.
“They’re not going to treat someone who comes into the hospital with type O differently than type A,” he said. “The differences are just not that large.”
A second, smaller study out of Canada looked at the severity of the infection and how that correlated with blood type:
Researchers in Canada found that among 95 patients critically ill with Covid-19, a higher proportion with blood type A or AB — 84% — 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.
So the larger study found blood type was not a factor in hospitalization or death but the smaller study found it was a factor in severity of the infection for those in the hospital. Those two findings seem to be at odds since people who go on a ventilator or remain in the ICU longer seem more likely to die. This is one of those situations where we’ll probably have to wait for a few more studies to be sure.
Dr. Mypinder Sekhon, the author of the Canadian study, told CNN “I don’t think this supersedes other risk factors of severity like age and co-morbities and so forth. If one is blood group A, you don’t need to start panicking. And if you’re blood group O, you’re not free to go to the pubs and bars.”