A blood vial
Before Covid-19, scientists had detected a link between blood groups and susceptibility to infection © REUTERS

People with type O blood may be at a lower risk of catching coronavirus and being admitted to hospital by the disease, according to a study from 23andMe, the genetics testing company.

Preliminary data from a study of more than 750,000 participants showed that people with type O blood were 9-18 per cent less likely to have tested positive for Covid-19. 

Individuals who had been exposed to the virus — including healthcare and frontline workers — were 13-26 per cent less likely to test positive, according to the data, which has not yet been peer reviewed or published in a medical journal.

The 23andMe researchers identified a variant in the ABO gene, which encodes for different blood groups, that may have been responsible for the people who tested negative being at lower risk. They said the findings were also notable because Covid-19 has been associated with blood clotting and cardiovascular disease. 

“The study and recruitment are ongoing, with the hope that we can use our research platform to better understand differences in how people respond to the virus,” 23andMe said. “Ultimately, we hope to publish our research findings in order to provide more insight into Covid-19 for the scientific community.”

Researchers around the world are investigating whether genetics can provide answers to outstanding questions about Covid-19, including why some people suffer much more seriously from it than others.

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23andMe is combining the database it has collected from selling direct-to-consumer genetic tests with surveys from customers. This includes information on whether they had been tested for or hospitalised by the virus and the nature of their symptoms.

The data follow two other studies, yet to be peer-reviewed, that have linked the development of the disease to the ABO gene. One in China found that the O blood group was associated with a lower risk of acquiring Covid-19. 

Another, from scientists at Columbia University in New York found it was only people with the O-positive blood type that were less likely to have a confirmed case of Covid-19. The 23andMe study found no difference between the O-positive and O-negative blood types. 

Before Covid-19, scientists had detected a link between blood groups and susceptibility to infection, for example, in malaria. Blood groups can be receptors for viruses, toxins or parasites — or serve as ‘false receptors’, preventing them from binding to tissue. 

The effects of having type O blood were still seen when adjusted for age, gender, ethnicity, body mass index and underlying conditions. There was little variation between other blood types. 

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