People with certain blood types may have a reduced risk of contracting coronavirus and even with the infection, be less susceptible to experiencing severe symptoms, new studies have shown.

According to two studies published in "Blood Advances" — a peer-reviewed, online only, open access journal of the American Society of Hematology (ASH) — there is some evidence that there may be a link between blood type and vulnerability to COVID-19.

The findings of the two studies are outlined below:

Fewer coronavirus patients with blood type O

A retrospective study of individuals tested for coronavirus showed that blood type O "may offer some protection against COVID-19 infection".

When researchers parsed through data from the Danish health registry of more than 473,000 people tested for COVID-19 and compared it to a control group of over 2.2. million people from the general populace, they found that among COVID-positive patients, there were fewer with blood type O and more with blood types A, B and AB.

This lends credence to the fact that people with blood type A, B and AB, may be more at risk of getting infected than those with blood type O.

Between the blood types A, B and AB, no significant difference in rates of infection was found.

Severe symptoms for people with blood types A, AB

A separate retrospective study showed that blood groups A and AB "appear to exhibit greater COVID-19 disease severity than people with blood groups O or B".

Researchers looked at data from 95 critically ill and hospitalised COVID-19 patients in Vancouver, Canada. It was found that those with blood types A or AB "were more likely to require mechanical ventilation, suggesting that they had greater rates of lung injury from COVID-19".

It was also found that more patients with groups A and AB needed dialysis for kidney failure.

What does this mean?

The two studies together show that blood groups A and AB are particularly at risk of organ failure due to COVID-19 as compared to blood types O and B.

Also, people with type A and AB did not require a longer duration of hospitalisation but did remain in the intensive care unit (ICU) for longer on average, compared to people with types O or B, indicating a more severe form of COVID-19.