Blood type may play role in severe Covid-19

Covid numbers in Andalucia on Tuesday, April 5.

Scientists have been battling to understand why some people suffer from severe Covid-19 whilst others appear to have little or no symptoms, with the latest research suggesting blood type may play a role.

Right from the outset certain groups were known to be susceptible to the virus, the elderly, the infirm and those with compromised immune systems. But no one understood why some people were seemingly immune whilst others became severely ill or died. What scientists really didn’t understand was why seemingly healthy people who were not in the high risk categories got severely ill or died.

What puzzled them is that people in the same family often had very different reactions to the virus.

Blood type

A group of scientists at Kings College London think they may have uncovered at least one of the mysteries. They believe that it has to do with genetics and more specifically blood type.

The group’s study, which was recently published in PLOS Genetics, analysed more than 3,000 protein samples that are causally linked to the severe development of the disease. Using a genetic tool to screen the proteins, the scientists found that six could be linked to severe development of the disease and eight that potentially protected a person from the disease.

One of those proteins determines blood groups, which according to the scientists suggests that blood group types play an instrumental role in the severity of the infection.

Co-first author Alish Palmos said: “We have used a purely genetic approach to investigate a large number of blood proteins and established that a handful have causal links to the development of severe Covid. Homing in on this group of proteins is a vital first step in discovering potentially valuable targets for development of new treatments.

“Assessing how blood proteins are linked to disease can help understand the underlying mechanisms and identify potential new targets for developing or repurposing drugs.”

Co-first author Vincent Millischer, from the Medical University of Vienna, explained: “Causality between exposure and disease can be established because genetic variants inherited from parent to offspring are randomly assigned at conception, similar to how a randomised controlled trial assigns people to groups.”

Millischer explained that in the study the groups are defined by their genetic propensity to different blood protein levels. ”This allows an assessment of causal direction from high blood protein levels to Covid severity, whilst avoiding influence of environmental effects”.

The study, which looked at two levels of severity – hospitalisation and respiratory support or death, identified that ABO, which determines blood group, was causally associated with an increased risk of hospitalisation and a requirement for respiratory support.

This backs up previous findings around the association of blood group with higher likelihood of death.

Blood group type and Covid-19

When considered together with other research into the virus and its effects, showed that those with blood group A needed to be investigated further. The suggestion is that this blood type is the one least likely to result in the individual experiencing less severe symptoms.

Gerome Breen, a Professor of Genetics, said: “What we have done in our study is provide a shortlist for the next stage of research. Out of thousands of blood proteins we have whittled it down to about 14 that have some form of causal connection to the risk of severe Covid.”

The finding that blood type may play role in severe Covid-19 requires further research to both confirm causality and to fully understand why this might be the case, and therefore what new preventative therapies could be developed.

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Written by

Peter McLaren-Kennedy

Originally from South Africa, Peter is based on the Costa Blanca and is a web reporter for the Euro Weekly News covering international and Spanish national news. Got a news story you want to share? Then get in touch at