Several preliminary studies have been published that propose a relationship between blood type and severity of COVID-19 symptoms.
A preliminary study conducted by researchers in Germany and Norway, which examined the genomes of 1610 individuals hospitalised with COVID-19, found that people with type A blood were 50% more likely to need oxygen or ventilatory support. In contrast, people with blood type O appeared to have an approximately 50% reduced risk of severe symptoms of COVID-19. However, the study’s authors were unable to say with certainty whether blood type itself or a risk factor linked to blood type is responsible for severity of symptoms.
A preliminary study undertaken in China looked at the blood types of more than 2170 people with confirmed COVID-19, of whom 206 died. Among those who died, 85 (41%) had blood type A. People with blood type A were also found to be more vulnerable to infection, and went on to develop more severe symptoms of COVID-19. In contrast, individuals with blood type O were described as being at ‘significantly lower risk’ of contracting COVID-19.
Similarly, a study conducted in the US examined over 1550 individuals tested for COVID-19—682 tested positive for the disease, of whom 33% had blood type A. The study found that individuals with blood types O-negative and O-positive were less likely to test positive for COVID-19 than people with other blood types.
These studies suggest that it is necessary to take blood type into consideration in the treatment of patients with COVID-19. The findings of these studies may be particularly significant because 38% of people in the UK have blood type A and blood type was found to be associated with disease severity in the 2002–2003 severe acute respiratory syndrome outbreak.