In the first study, researchers compared Danish health registry data from over 473,000 individuals tested for Covid-19 to data from a control group of more than 2.2 million people from the general population. Among the Covid-19 positive, they found fewer people with blood type O and more people with A, B, and AB types. The study suggests that people with blood types A, B, or AB may be more likely to be infected with Covid-19 than people with type O.
The researchers did not find any significant difference in rate of infection between A, B, and AB types. “It is very important to consider the proper control group because blood type prevalence may vary considerably in different ethnic groups and different countries,” said study author Torben Barington from University of Southern Denmark.