Study Reveals Causal Link between Blood Type and COVID Severity

Early in the pandemic doctors began tracking the association between COVID-19 disease severity and a patient’s blood type. Researchers have validated those early observations, finding that several blood proteins are Causal linked to an increased risk of hospitalization and death from COVID-19.The earliest observational studies to come out of Wuhan in 2020 pointed to a correlation between a person’s blood type and their risk of serious illness from a SARS-CoV-2 infection.

The general observation was that those with type A blood seemed to be at a much higher risk of hospitalization and death than those with type O blood. A new study was published in the journal PLOS Genetics.The study has offered insight to date into the Causal relationship between blood type and COVID-19 severity. The research used an analytical method called Mendelian randomization to assess the relationship between the gene variants that govern levels of blood proteins and COVID-19 disease outcomes.

The study author said that the Causal between exposure and disease could be established because genetic variants inherited from parent to offspring are randomly assigned at conception similar to how a randomized controlled trial gives people to groups. In our study, the groups are defined by their genetic propensity to different blood protein levels, allowing an assessment of Causal direction from high blood protein levels to COVID-19 severity while avoiding the influence of environmental effects.

The researchers screened over 3,000 blood proteins, and COVID-19 severity was determined by either hospitalization or death. One of the key findings was a Causal association between COVID-19 severity and an enzyme known as ABO, which defines a person’s blood type. Christopher Hübel from King’s College London said the new research did not interrogate the relationship between specific blood types and COVID-19 severity. However, he does point out the ABO findings do validate prior observational studies linking type A blood with an increased COVID-19 risk.