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.
A new European study involving 1,980 patients with Covid-19 revealed people with blood group A had a higher risk of catching coronavirus and developing severe symptoms than other blood groups. However, among those with blood group O, there appeared to be some form of “protective effect”.
Previous studies have shown similar findings. A preprint study of 2,173 patients with Covid-19 in China found people with blood group A were at a higher risk of contracting the disease, while people with blood group O had a lower risk of infection.
Another preprint study involving 1,559 coronavirus patients in New York found those with blood group A were 33% more likely to test positive for Covid-19 than other blood types, and those with O-negative and O-positive blood types were less likely to test positive.
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 inhibit, 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.
Should people with blood type A be worried?
Dr Vaiyapuri says while the new study is high quality, it “does not provide strong evidence” that blood group type can lead to more severe Covid-19.
He pointed out that no one has so far reported that those with blood group O are 100% protected against the virus and those with blood group A are 100% susceptible. “Only a small percentage of protection/susceptibility clearly demonstrates that there are several other factors associated with this disease, and therefore further research is required to establish this link,” he says.
Professor Danny Altmann, from Imperial College London’s Department of Medicine, adds that in terms of the study, “there’s not much you can do in terms of behavioural change, knowing that you’re slightly higher or lower risk”. But he does say the findings “open doors to whole new directions for medical research and drug discovery to try and explain how the blood-group effect may be working”.
People with A blood group should not panic about these results, and at the same time, those in the O blood group should not be too relaxed about it, says Dr Vaiyapure. Everyone should continue to stick to the lockdown rules: social distancing, washing hands regularly, not touching your face when out in public and wearing face covers where social distancing isn’t possible.
He concludes: “Everyone should follow the guidelines provided by the health authorities and be extremely cautious to protect themselves and others around them.”
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.