Blood type may play a role in the risk of becoming infected with COVID-19 or developing severe complications, suggested two studies published Wednesday.

Two studies on the matter were published in the journal Blood Advances. It is a publication of the American Society of Hematology (ASH).

In the first research, they found that blood type O was linked with reduced risk to a COVID-19 infection. But this did not mean one blood type can protect a person more.

Even someone with a blood type O can and do become infected by COVID-19, they said. The researchers looked at data from 473,654 people who tested for COVID-19 in a six-month period. They were only able to analyze 7,422 positive tests.

In the second study, the earlier findings were also supported. Canadian researchers analyzed data on 95 COVID-19 patients in Vancouver from February to April. All patients were hospitalized or sent to intensive care.

They found that people with the blood type O has less likelihood of getting severely ill. Just like the findings of the earlier research, this study doesn't suggest that other blood types pose significant danger.

(Photo : Guillermo Legaria/Getty Images)
View of stored boxes containing blood samples of COVID-19 patients on August 14, 2020 in Bogota, Colombia.

Dr. Roy Silverstein, chair of medicine at the Medical College of Wisconsin, told NBC News that type O has a "slightly lower risk...but it's a small decrease."

He added that blood type does not mean a person has zero risk of contracting the virus.

Silverstein also pointed out that blood type does not change how patients get treated for COVID-19, saying the difference is "not that large."

Silverstein was not involved in the new studies but was a former president for the ASH.

Further Research on Blood Types Needed

Experts say there is still further research needed to verify this information. Their research raised more questions as to why there is a link at all and what implications it has, if it has any, to patients.

Their findings were also limited because not all tests were given blood type information. Only 62% of those who were tested had available blood type information.

Dr. Torben Barington, senior author of the first study, reminded people not to worry about the findings.

"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," he told CNN.

He noted that if scientists ever find out what the link is, it may play a role in proactive treatment of patients.

Dr. Mypinder Sekhon, an author of the second study, said one possible factor may be clotting.

Blood type O has less of a key clotting factor, making them less prone to blood coagulation problems. In COVID-19 patients, clotting can be a major driver for the illness' severity.

Other explanations could be antigens in blood groups that affect the production of antibodies or genes associated to blood types.

As constantly reminded, public health officials said people of any blood type still have to take the necessary safety precautions. Wearing a mask, physical distancing and proper hand washing are still key in preventing COVID-19.

Health experts also reminded people that the studies only suggested an association between blood types and COVID-19 risks. They do not present a cause-and-effect scenario.

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