Covid-19: Reduced risk for those with blood type O

People with blood type O are, on average, 12% less likely to be infected with coronavirus than other blood types. Also, those with negative blood types (O-, A-, B-, or AB-) have a 21% lower risk of contracting coronavirus than those with positive blood types, according to a new Canadian scientific study.

Furthermore, individuals with blood type O are 13% and 19% less likely to develop severe symptoms of COVID-19 or die from the disease, respectively. Therefore, those with negative blood type O- appear to have the lowest risk of all.

According to National Blood Donation Center, The most common blood type in Greece is O+, and the rarest is AB-. According to Wikipedia, it is estimated that in our country, the distribution of people into blood groups is approximately as follows: O+ 37%, A+ 33%, B+ 11%, O- 7%, A- 5%, AB+ 4%, B- 2%, and AB- 1%. Consequently, those with negative blood types constitute a total of approximately 15%, while those with type O constitute 44%.

The Canadian study also shows that the risk of SARS-CoV-2 infection is 15% higher for group AB than for group A and 5% lower for group O than for group A, a percentage that increases to 12% on average compared to the other three groups combined. Those with group B face a 21% greater risk of severe Covid-19 than those with group A.

The researchers, led by Dr. Joel Ray of the Department of Medicine at the University of Toronto and St. Michael's Hospital, who published their findings in the American medical journal «Annals of Internal Medicine,» analyzed blood test data from 225,556 people with an average age of 54, as well as coronavirus test samples. Of these, 44% had group O, 36% had group A, 15% had group B, and 5% had group AB.

The findings of the Canadian study are generally consistent with those of an earlier Chinese study, which was the first to find that not all blood types have the same risk of coronavirus infection. The Chinese study of 2,173 Covid-19 patients in three hospitals in Wuhan and the surrounding Hubei region found that the Covid-19 death rate was higher in blood group A (41% of total deaths), while the proportion of people with the same blood type in the Wuhan population did not exceed 34%. On the other hand, the death rate of people with Covid-19 in group O was lower (25%) compared to the percentage of group O in the general population (32%).

Every person belongs to one of eight blood groups. These groups are subcategories of the four main groups of the ABO system (A, B, AB, or O). The Rhesus (Rh) system further divides these four groups into Rh positive (+) or Rh negative (-), creating eight basic blood types or groups: O-, O+, B-, B+, A-, A+, AB-, or AB+.

The Rhesus system was discovered in 1939 and is based on the presence of antigens, mainly the D antigen. Antigens are molecules that bind to an antibody. A person may or may not have the Rh factor (D antigen) on the surface of their red blood cells, in which case they are classified as Rh-positive (Rh+) or Rh-negative (Rh-).

Not all blood types are compatible with each other. This is due to the different antibodies that each person has depending on their blood type. Those with blood type O are considered «universal donors.» and their blood can be given to any patient regardless of their blood type. On the contrary, Those with AB+ blood type are «universal donors.», so they can take blood from all groups.