People with blood type O are less likely to catch coronavirus, study claims

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People with blood type O are less likely to catch Covid-19, according to new research. Their risk of severe complications such as organ failure - and even death - is also reduced, say scientists. But individuals with blood types A and AB are most vulnerable, suggest the findings.

The findings from two independent studies shed fresh light on why the virus is deadly for some - while others are not even aware they have had it. One team compared Danish health registry data of over 473,000 individuals tested for Covid-19 to a control group of more than 2.2 million from the general population.

There were fewer positive results among those with blood type O - the most common - and more in peers with A, B and AB. Rates of infection were similar in these three groups. The trends remained after the researchers took into account ethnicity which affects blood group distributions.

Lead author Dr Torben Barington, of Odense University Hospital, said: "It is very important to consider the proper control group because blood type prevalence may vary considerably in different ethnic groups and different countries. "We have the advantage of a strong control group - Denmark is a small, ethnically homogenous country with a public health system and a central registry for lab data. So our control is population-based, giving our findings a strong foundation."

A second study of 95 critically ill Covid-19 patients in hospital in Vancouver found the A and AB blood types were at higher risk of severe symptoms than those with O or B. They were more likely to require mechanical ventilation - suggesting they had greater rates of lung injury from the virus - and dialysis for kidney failure.

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It suggests these two blood groups have an increased risk of organ dysfunction or failure due to Covid-19.

What's more, while people with blood types A and AB did not have longer overall hospital stays they remained in the intensive care unit (ICU) for longer on average . This may also signal a greater Covid-19 severity level, said the Canadian team.

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.

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"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."