It’s looking increasingly likely that having blood type O might give you some protective effects against Covid-19, while blood type A may be linked to more severe illness from the virus.
Two new studies published in the journal Blood Advances suggest people with blood type O might have a lower risk of Covid-19 infection and reduced likelihood of becoming severely ill. Previous studies have also noted the pattern.
What did the studies find?
One of the studies compared Danish health registry data from more than 473,000 individuals tested for Covid-19 to data from a control group of more than 2.2 million people from the general population.
They found fewer people with blood type O tested positive for the virus, and more people with A, B, and AB types did. This led them to suggest people with blood type O might be less likely to become infected with the virus than those with blood types A, B, or AB.
There wasn’t any significant difference in the rate of infection between A, B, and AB types, the researchers found.
Another European study involving 1,980 patients with Covid-19 based at seven hospitals in Italy and Spain unearthed a similar pattern and revealed people with blood group A had a higher risk of catching coronavirus and developing severe symptoms than other blood groups. Among those with blood group O, there appeared to be some form of “protective effect”.
Another set of researchers examined data from 95 critically ill Covid-19 patients hospitalised in Vancouver, Canada, and found people with blood groups O or B appear to suffer less severely than those with blood groups A or AB if they do contract the virus.
They found that patients with blood groups A or AB were more likely to require mechanical ventilation, suggesting that they had greater rates of lung injury from Covid-19. They also found more patients with blood group A and AB required dialysis for kidney failure.
“The unique part of our study is our focus on the severity effect of blood type on Covid-19,” said study author Mypinder Sekhon, of the University of British Columbia. “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.”
Why might this be happening?
There are four main blood groups. These are:
Blood group A, which has A antigens on the red blood cells with anti-B antibodies in the plasma.
Blood group B, which has B antigens with anti-A antibodies in the plasma.
Blood group O, which has no antigens, but both anti-A and anti-B antibodies in the plasma.
Blood group AB, which has both A and B antigens, but no antibodies.
Previous research into other forms of coronavirus found that certain antibodies linked to blood group O helped to fight off the virus better than others.
“People have seen that O blood group people are likely to be more protected against Sars-CoV previously compared to people with A blood type,” explains Dr Sakthivel Vaiyapuri, associate professor in cardiovascular and venom pharmacology at the University of Reading. “This was suggested to occur due to the presence of anti-A and anti-B antibodies in people with O blood group.”
Doctors at a Hong Kong hospital reported that anti-A antibodies were able to prevent, or even block, the binding of the virus to the host cell, which may provide some explanation as to why being in the O blood group could offer more protection.
How do you find out what blood group you are?
If you are don’t already know what blood group you are, you can ask your GP – however you will only be able to find out if you’ve previously had a sample of blood taken and tested.
Failing that, you can find out your blood type if you give blood. People who already do this should have their blood type recorded on their official NHS Blood & Transplant donor card.