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People with blood type O may have lower risk of Covid-19 infection and severe illness, studies suggest

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People with blood type O may be less vulnerable to Covid-19 and have a reduced likelihood of getting severely ill from the virus, according to two new studies.

The two independent studies, carried out by researchers in Denmark and Canada and published in the journal Blood Advances, found that individuals with blood types A and AB are most vulnerable to the disease.

The research provides further evidence that a person’s blood type may play a role in their susceptibility to coronavirus and could shed further light on why the illness proves deadly for some but others only experience mild symptoms, or none at all.

In the Danish study, researchers found that among 7,422 people who tested positive for Covid-19, only 38.4 per cent were blood type O.

This is despite people with that blood type making up 41.7 per cent of a control group of 2.2 million people from the general population who were not tested.

By comparison, 44.4 per cent of those who were blood type A tested positive, while in the wider control group that blood type made up 42.4 per cent.

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Lead author Dr Torben Barington, of Odense University Hospital, said: “We do not know whether this is some kind of protection of group O, or whether it’s some kind of vulnerability in the other blood groups.”

He added: “I think this has scientific interest, and when we find out what the mechanism is, perhaps we’re able to use that proactively in some way in regard to treatment.”

The Canadian study meanwhile found those with blood type A or AB were at higher risk of experiencing severe Covid-19 symptoms than those with O or B.

Analysis of 95 critically ill Covid-19 patients in a Vancouver hospital revealed people in the first category were more likely to require mechanical ventilation and dialysis for kidney failure.

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People with blood type A or AB also had a longer stay in the hospital’s intensive care unit on average, at a median of 13.5 days, compared with those with blood group O or B, who stayed for a median of nine days.

Lead author Dr Mypinder Sekhon, of the University of British Columbia, said: “The unique part of our study is our focus on the severity effect of blood type on Covid-19.

“We observed this lung and kidney damage, and in future studies, we will want to tease out the effect of blood group and Covid-19 on other vital organs.

“Of particular importance as we continue to traverse the pandemic, we now have a wide range of survivors who are exiting the acute part of Covid-19, but we need to explore mechanisms by which to risk stratify those with longer-term effects.”

While there are several theories, researchers don’t yet know what mechanism could explain the link between different blood groups and coronavirus.

Scientists say the reasons for this link are not yet clear and more research is needed to say what implications, if any, it has for patients.

Experts have long said age and weight are key factors in how severely impacted coronavirus patients are.

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