Is there a link between blood type and severe COVID-19? Study says maybe

Researchers believed early in the COVID-19 pandemic that a person’s blood type may be linked to the chance that they would have a more severe outcome should they contract the novel coronavirus.

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A study released on Monday reinforced that theory with findings showing that several blood proteins, including the enzyme that determines blood type, are linked to an increased risk of hospitalization and death from COVID-19.

Researchers used a study method called Mendelian randomization which allows scientists to study the relationship between gene variants that control levels of proteins in the blood and COVID-19 disease outcomes.

The researchers screened more than 3,000 blood proteins and found among other things that ABO, an enzyme that determines a person’s blood type, had an association with severe COVID-19 outcomes.

“The enzyme helps determine the blood group of an individual and our study has linked it with both risk of hospitalization and the need of respiratory support or death,” according to Christopher Hübel from King’s College London. Hubel is one of the study’s authors.

“Our study does not link precise blood group with risk of severe COVID-19 but since previous research has found that proportion of people who are group A is higher in COVID-19 positive individuals, this suggests that blood group A is more likely candidate for follow-up studies.”

Early studies indicated that those in the Type A blood group seemed to have more severe cases of COVID-19 while those in the Type O group tended to have fewer severe outcomes.

Whether blood type is a factor in a more severe course of the disease or not has been debated.

Two studies published last year suggested that blood types have no connection to hospitalization or death from COVID-19. The studies, one from Massachusetts General Hospital in Boston and one from Columbia Presbyterian Hospital in New York City, did not find significant evidence that blood type meaningfully affects COVID-19 risk

The study, which has been peer-reviewed, was published in the journal PLOS Genetics on Monday.