A pair of new studies suggest that those with a certain blood type may be less likely to be infected with the novel coronavirus and less likely to suffer severe illness if they were to be infected.
The studies were both published in the journal Blood Advances, a publication of the American Society of Hematology, on Wednesday. In the first, researchers looked at some 473,654 people in Demark who were tested for COVID-19 between February and July and compared them with the general population of roughly 2.2 million people. (For context, about 7,422 results were positive.)
Interestingly, the researchers found that among those who tested positive for the virus, a lower percentage had type O blood, while a higher percentage had blood types A, B, or AB.
The researchers in the first study said their findings “demonstrate that blood group O is significantly associated with reduced susceptibility to SARS-CoV-2 infection,” though noted that their study did have several limitations, including the fact that “ABO blood group information was only available for 62% of all tested individuals, and only doctors and nurses were identified as health care personnel.”
In the second study, researchers looked at 95 critically ill COVID-19 patients in Canada from February to April, finding that blood type appeared to play a role in the severity of their illness.
"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," they wrote.
The studies bolster past research on how a person’s blood type may affect their risk of contracting the virus.
In June, preliminary results from an ongoing study conducted by the genetic testing firm 23andMe suggested that those with type O blood may have some protection against the novel coronavirus. In fact, early results indicated that people with type O blood were between 9% and 18% less likely to test positive for COVID-19 when compared to the other blood types.
“These findings hold when adjusted for age, sex, body mass index, ethnicity, and co-morbidities,” the company noted, adding that there “appeared to be little differences in susceptibility among the other blood types.”
Additionally, a study out of China that was published in March also found that those with type O blood may be more resistant to SARS-CoV-2, while those with type A blood might be more at risk.