If there’s anything we want to know about COVID-19, it’s probably this: What is my risk of getting it?
Researchers have identified certain things that make some people more vulnerable than others. Men are at greater risk than women. Older people are at higher risk than younger people. Those with chronic health problems like type 2 diabetes, obesity, and serious heart conditions are worse off than those without them. Blacks and Latin Americans are at greater risk than Asians and whites.
There is now evidence that blood type could also be a risk factor.
A handful of studies have suggested that people with some blood types are more likely to be hospitalized with COVID-19, while those with other blood types are less likely to require that level of care. The most recent evidence was published last month in the New England Journal of Medicine.
Here is a look at what scientists have learned about blood type and its role in the COVID-19 pandemic.
How many blood types are there?
Eight. Yours is determined in part by the presence (or absence) of A and B antigens in your red blood cells. If you only have A antigens, your blood type is A. If you only have B antigens, your blood type is B. If you have both, your blood type is AB, and if you don’t have either, your blood type is O.
Also, red blood cells may have a protein called Rh factor. If you have it, you are Rh positive; if not, you are Rh negative.
The combination of A and B antigens and Rh factor produces the eight main blood types: A-positive, A-negative, B-positive, B-negative, AB-positive, AB-negative, O-positive and O- negative.
What did the New England Journal of Medicine study say about blood types?
The researchers analyzed genetic data from more than 1,600 hospitalized patients with severe cases of COVID-19 in Italy and Spain and compared it to 2,200 others who did not have the disease. After making adjustments to account for the effects of age and sex on the risk of COVID-19, the researchers found striking differences in the blood types of sick patients compared to controls.
In this population, having type A blood was associated with a 45% higher risk of having severe COVID-19. On the other hand, having type O blood was associated with a 35% lower risk of the disease. Those relationships were maintained if the Italian and Spanish patients were analyzed separately or together.
No other blood group was associated with a higher or lower risk of the disease. Also, blood type did not appear to be related to the risk of needing a mechanical respirator.
The study design did not allow the researchers to determine if the blood type was associated with the risk of coronavirus infection or, if infected, with the risk of becoming seriously ill.
“The hope is that these and other findings to come point the way to a deeper understanding of the biology of COVID-19,” wrote Dr. Francis Collins, geneticist and director of the National Institutes of Health, on his blog. . “They also suggest that a genetic test and a person’s blood type could provide useful tools to identify those who may be at increased risk for serious disease.”
How does that align with other research?
At least two other groups have looked for links between blood type and COVID-19 risk and have found similar results.
The first hint that blood type might have something to do with disease risk came in March from researchers in China, who compared 2,173 COVID-19 patients at three hospitals in Wuhan and Shenzhen with more than 27,000 “normal people” . They found that people with type A blood had a 21% higher risk of the disease than their counterparts with other blood types, and that people with type O blood had a 33% lower risk.
The following month, a team from Columbia University examined 1,559 people in the New York City area who were examined to see if they were infected with the coronavirus that causes COVID-19. They found that having type A blood was associated with a 34% higher probability of testing positive, while having type O blood was associated with a 20% lower probability of testing positive. Additionally, people with type AB blood were 44% less likely to test positive, although only 21 of the 682 people who tested positive for the coronavirus had AB blood.
The Columbia researchers noted that their findings on the risks associated with type A and type O blood were consistent with the results from China, despite the fact that the distribution of blood types was significantly different in populations of New York, Wuhan and Shenzhen.
Both reports were published on the MedRxiv website, where the researchers share preliminary data before they have undergone a peer review.
Why does blood type have something to do with COVID-19?
That is not clear. Perhaps different combinations of A and B antigens change the immune system’s production of antibodies to fight infection or have some other unknown biological effect, the authors of the New England Journal of Medicine wrote.
Another possibility is that genes associated with blood type also affect the ACE2 receptor in human cells, which the coronavirus searches for and binds to, they wrote.
How can I know what my blood type is?
Your doctor may have it on file if it has been tested in the past.
If not, you can try it at home with a kit that includes an Eldoncard. The kit will require you to prick your finger to obtain a small blood sample, then mix it with antibodies against the A and B antigens that come on the card. If your red blood cells contain A or B antigens, they will react with the antibodies and clump together on the card.
If you only see a reaction to antibodies A, your blood type is A. The same goes for antibodies B. If you see a reaction to both, your blood type is AB, and if there is no reaction, your blood type is OR.
An additional circle on the card contains antibodies against the protein called Rh factor. A reaction there indicates that you are Rh positive; if nothing happens, you are Rh negative.
If that seems like too much trouble, you can donate blood. If you go to the Red Cross, they will send you a donor card that indicates your blood type.
Should I take extra precautions if my blood type is A?
Everyone should be as careful as possible at all times, regardless of blood type. (That also applies to people with type O blood.)
If you have been outside or have been in contact with high contact surfaces, wash your hands for at least 20 seconds. Wear a mask if you are leaving your home, and keep at least six feet between you and others who are not members of your household. Try not to touch your face so that the virus cannot sneak into your body through your eyes, nose or mouth. And be sure to clean door knobs, faucets, phones, and other frequently touched surfaces every day.
For more tips on staying safe, follow these tips from the Centers for Disease Control and Prevention.