The results also reveal that those with a negative blood type (O-, A-, B-, or AB-) are, on average, 21% less likely to contract the virus compared to people with the positive type.
Individuals with type O or negative blood were 13% and 19% less likely to have severe symptoms or death, respectively.
The study says that about one in eight people (13%) who carry O- are 26% less likely to have the infection and 28% less likely to have severe symptoms or death.
Researchers from the Institute of Clinical Osteopathic Sciences in Toronto studied 225,556 people who took a blood test between 2007 and 2019 and a “Covid-19” swab this year.
Every person has one of four blood types, either A, B, AB, or O. The difference in blood groups depends on the presence or absence of specific attachments on the red blood cells called antigens. And the presence or absence of these antigens is what determines a person’s blood type.
The researchers analyzed the medical records of more than 225,000 participants who had taken the ABO blood type test and the SARS-CoV-2 test, and of these, 36.3% had blood type A, 4.5% had AB, 14.9% had B, and 44.3%. % Have type O.
The statistical analysis took into account all other variables and comorbidities, and found that the relative risk of SARS-CoV-2 infection is 15% higher in type AB compared to type A.
The researchers also found that the risk of infection with type O is 5% less than with type A, but when compared to all blood types, this increases to 12%.
There were 1,328 cases of COVID-19 with severe disease or death, the researchers wrote, with a higher likelihood between blood groups AB and B as well as those with Rh + (positive Rh blood group system).
And people who have blood type B have a 21% risk of developing a serious disease after infection with “Covid-19″, of those who have type A.
In this study, which was conducted within a comprehensive health care system with a large-scale SARS-CoV-2 test, O blood groups and the Rh− blood system were associated with a slightly reduced risk of developing SARS-CoV-2 infection as well as severe Covid-19 disease. Death from it, ” according to the results of the study published in Annals of Internal Medicine.
The results are consistent with previous research from China that found a similar protective effect for some blood types.
The researchers evaluated 2,173 people diagnosed with the coronavirus, including 206 people who died after contracting the virus, from three hospitals in Hubei.
Academics compared the data of infected Wuhan patients with 3,694 uninfected people in the same region.
Of the 206 patients who died, 85 had type A blood type, which equates to 41% of all deaths.