A growing body of evidence suggests those who have blood type O may be less likely to contract coronavirus and typically experience less severe symptoms when they do come down with the illness.

While a pair of new studies, published Wednesday in health journal Blood Advances, suggests blood type can be tied to COVID-19, experts said the way patients are being treated will not yet change. They noted it’s not clear what the exact link between the two is, adding that more research is needed.

In the first study, scientists in Denmark analyzed data from 473,654 people tested for the virus between February and July, CNN reported. Most results were negative, with just 7,422 tests returning positive. Of those, only 38.4 percent had blood type O — despite people with that blood type making up 41.7 percent of the roughly 2.2 million untested people in the population.

People with type A blood, however, accounted for 44.4 percent of the infected patients, the study found, despite making up 42.4 percent of the untested group.

“Blood group O is significantly associated with reduced susceptibility to SARS-CoV-2 infection,” researchers wrote, according to NBC News.

In a second study also published on Wednesday, Canadian scientists examined 95 COVID-19 patients in Vancouver between February and April. All were sick enough to be hospitalized in intensive care units.

Their research showed those with blood type A or AB typically had a longer stay in the intensive care unit, with a median of 13.5 days. Meanwhile, people with blood group O or B, experienced a visit in the ICU with a median of about nine days.

“A higher proportion of COVID-19 patients with blood group A or AB required mechanical ventilation and had a longer ICU stay compared with patients with blood group O or B,” the study authors wrote.