The link between blood type and COVID severity

A recent study coauthored by Canadian Blood Services’ chief scientist, Dr. Dana Devine, shows that people with blood groups A or AB are more likely to have a severe COVID infection than people with blood groups B or O.

The study looked at 95 patients critically ill with the SARS-CoV-2 virus in the intensive care units (ICUs) of two major Vancouver hospitals. Among them, 84 per cent of COVID patients with blood type A or AB needed to be put on a ventilator, compared to 61 per cent of patients with blood type O or B.

People with blood types A or AB were also in the ICU for longer. The most common length of stay in the intensive care unit for patients with blood type A or AB was 13.5 days, while those with type O or B most commonly stayed for nine days.

This finding adds to growing evidence that blood type plays a role in COVID severity. But, blood type seems to be a minor risk factor compared to advanced age or having underlying medical conditions.

“If you have type A blood, you don’t need to be terrified. And if you’re type O, you shouldn’t hear this and think you can take more risks,” says Dr. Devine. “More research needs to happen to understand this phenomenon better.”

Blood types are defined by the proteins and sugar molecules on the surface of red blood cells. The most important and well-known blood group system is ABO, which categorizes blood types as A, B, AB, and O. In addition to these blood groups, people’s blood can be positive or negative for something called the Rh factor, for example making them O+ or O-.

Visit our COVID-19 portal to learn more about how Canadian Blood Services is responding to the pandemic.