New research suggests that people with O blood type are less likely to contract the novel coronavirus. For such blood type, the risk of developing severe symptoms, including organ failure, is also reduced.


However, people who have blood types A and AB are the most vulnerable to the infection.

The findings of two separate studies aimed to reason why the virus is lethal for some, while others are not even aware they have had it.

The study was published in the journal Blood Advances .

Changes in red blood cells can help identify Covid-19 severity level: Study

First study

The first team gathered information from the Danish health registry data of more than 4,73,000 Covid-19 positive individuals out of the general population of 2.2 million.

The findings revealed that there were fewer positive results among those with blood type O — the most common while peers with blood type A and AB were the most vulnerable. Rates of infection were similar in these three groups.

The trends remained unaffected after the researchers factored in ethnicity, which affects blood group distributions.

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Lead author Dr Torben Barington, of Odense University Hospital, said in a statement: “It is very important to consider the proper control group because blood type prevalence may vary considerably in different ethnic groups and different countries.”

He added: “We have the advantage of a strong control group — Denmark is a small, ethnically homogeneous 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.”

Second study

In the second study, the researchers examined 95 critically ill Covid-19 patients in a hospital in Vancouver.

They found that the A and AB blood types were at higher risk of severe symptoms than those with O or B.

The researchers observed that patients with these blood types are more likely to be put on mechanical ventilation. This suggested that they had greater rates of lung injury from the virus — and dialysis for kidney failure.

These patients also had an increased risk of organ dysfunction or failure due to Covid-19.

The researchers also noted that people with blood types A and AB did not have longer overall hospital stays. However, 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.”

The researchers noted in their study: “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.”