There are two theories about the connection between blood groups and coronavirus, according to Jacques Le Pendu, research director at Inserm, a French medical research body.
One is that people with type O are less at risk of coagulation problems and clotting has been found to have considerable influence on the severity of the disease.
He said it could also be due to the likelihood that the pathogen will carry the infected person’s blood group antigen.
As such, the antibodies generated by a person with blood group O might disable the virus when transmitted from a person with blood group A.
But he said: “However, this protection mechanism would not work in all situations.
“A blood group O person could infect another blood group O person for example.”