Researchers have been investigating whether certain factors make individuals more susceptible to SARS-CoV-2 infection and severe illness.
One potential factor of interest is blood type. Early studies from China in 2020 suggested that individuals with blood type A might be at a higher risk of infection, while those with type O may have some protection against the virus. However, different studies have yielded mixed results, leaving experts uncertain about the significance of blood type as a risk factor for COVID-19.
Dr. Sean Stowell, an associate pathology professor at Brigham and Women’s Hospital and Harvard Medical School, made an intriguing discovery while working with scientists at the U.S. Centers for Disease Control and Prevention. He found that the finger-like projections on the SARS-CoV-2 virus closely resemble the blood group proteins on human cells. These proteins serve as the entryway for the virus to bind to and infect human cells. The recognition of blood group proteins by the virus suggests that certain blood types may enhance their ability to infect cells, potentially explaining the role of blood type in COVID-19 risk.
Dr. Stowell and his team conducted experiments to explore this connection and published their findings in the medical journal Blood. They discovered that cells from individuals with blood type A were more susceptible to SARS-CoV-2 infection compared to cells from those with type O. Type O, being devoid of blood type proteins, can be universally donated without triggering an immune response in individuals with types A, B, or AB. On the other hand, types A, B, and AB contain different sets of proteins called antigens, which interact differently with the COVID-19 virus.
The studies revealed that type A blood was associated with a 25% to 50% increased risk of infection, depending on the specific variant involved. Notably, cells with type A blood were particularly vulnerable to infection by the Omicron variant. The affinity of SARS-CoV-2 for type A blood proteins is attributed to its ability to bind to cells with antigens from blood type A, making them more receptive to the virus. Although blood group A does not directly aid the virus in entering cells, the stickiness of these cells allows the virus to attach more easily and locate the ACE2 receptors necessary for infection.
While people with type A blood may be more cautious about exposure and potentially face a higher risk of severe disease if infected, it is not a definitive conclusion. Blood type is just one of many factors influencing COVID-19 risk and complications. Additionally, not all individuals with type A blood have the same amount of A group antigens or ACE2 receptors on their cells. Therefore, variability exists even among individuals with blood type A.
Similarly, individuals with type O blood should not assume they are entirely protected against COVID-19. Regardless of blood type, everyone should continue following safety precautions such as vaccination and mask-wearing during periods of rising infections. Blood type should not diminish the importance of adhering to standard preventive measures.
Nevertheless, this new understanding of how blood types may influence COVID-19 risk could assist doctors in managing risk among vulnerable groups like the elderly and immunocompromised individuals. Being aware of a patient’s blood type could prompt healthcare professionals to be more vigilant in monitoring signs and symptoms of infection and educating patients about protective measures.
Dr. Stowell plans to further investigate how individuals with type B blood, whose antigens differ only slightly from those with type A, are affected by COVID-19. The reasons behind the virus’s weaker binding to type B blood are yet to be determined but will be explored in ongoing research.
Regardless of blood type, everyone should remain cautious and follow recommended preventive measures to minimize the spread of the virus.
