“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. SARS-CoV-2 is the virus that causes Covid-19.

The findings of the study are limited because blood type information was available for just 62 percent of those who were tested.

It is also important to note that people with type O blood can and do become infected.

“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.