People with type A blood are at greater risk of contracting COVID-19 compared to those with type O, according to research published June 27 in the journal Blood.
Researchers first began investigating how blood type may affect COVID-19 infection risks in 2020, though the results from several small studies were mixed. The latest study shows people with type A blood are at a 25 percent to 50 percent higher risk of developing a COVID-19 infection depending on the variant, lead author Sean Stowell, MD, told Time.
Dr. Stowell, an associate professor of pathology at Harvard Medical School in Boston, embarked on the study after working with the CDC to develop a blood test for COVID-19. He learned that the SARS-CoV-2 virus contained similar proteins on its surface as those from blood groups on human cells. These proteins bind to human cells. If the virus recognizes blood group proteins, it could mean certain blood groups enhance the virus's ability to bind to and infect human cells, according to Time.
"Blood group A doesn't itself help the virus get into cells, but because it makes cells more sticky to the virus, the chance that the virus can find ACE2 receptors and get into cells is higher. Since the group A antigens are all over the place in someone with type A blood, the virus can land on a cell surface more readily than in someone with type O blood," Dr. Stowell told Time.
Blood type is one of many factors that influence the risk of getting COVID-19 or having severe complications, Dr. Stowell said, adding that people should still take appropriate precautions, regardless of their blood type.