A new study of more than one million people suggests those with a certain blood type are less at risk of contracting Covid-19 than others.
The study of 1.05 million participants over four months, published on medrxiv.org, has found people with O-type blood may be less susceptible to contracting coronavirus.
The results have not been peer reviewed.
The study is based on research results from personal genomics and biotechnology company 23andMe, which conducted the work this year.
It found people with O-type blood appear to be at a lower risk of being infected and also are less likely to have a severe case of the disease.
"Our data supports a role in susceptibility to infection, suggesting that blood group O is protective in contrast to non-O blood groups," the scientists wrote in their findings.
Interestingly, blood group AB did not show a different result to blood groups A or B.
The reason for a possible protective link between blood group O and the coronavirus isn't clear but the authors suggested a mechanism at the "binding and internalisation of Sars-CoV-2 viral particles" — meaning when the virus binds to the blood cell.
The study relied on web-based surveys where respondents self reported. The surveys included an initial baseline survey, and three subsequent surveys.
TechnologyNetworks.com noted self-reporting methods are subject to validity issues because the truthfulness of the subjects answers can't be confirmed.
"The evidence to date is still preliminary. It's interesting, and it's re-energised the debate about what the role of the blood group system is," Dr James McFadyen, Baker Heart and Diabetes Institute senior research fellow, told the Sydney Morning Herald.
"But none of these studies is definitive by any stretch."