Your Blood Type Could Affect How Sick You Get From COVID-19

 Since the start of the pandemic, researchers have tried to figure out what, exactly, makes some people more likely to develop severe COVID-19 while others develop more minor forms of the virus. And, while the Centers for Disease Control and Prevention (CDC) has compiled a long list of risk factors for developing severe COVID, there has been a lot of questions around how your blood type can influence things as well.

Now, a new study has found a link between COVID-19 severity and certain blood types. The paper, which was published in PLOS Genetics, analyzed more than 3,000 blood proteins to try to figure out which ones made someone more or less likely to develop severe COVID-19. (The researchers defined “severe” as being hospitalized, requiring help breathing, or death.)

The researchers found several potential blood proteins that seemingly raised your risk of severe COVID, including one that determines your blood type. The researchers say in the paper that “the precise blood group associated with the increased risk for hospitalization as a result of COVID-19 cannot be determined from our results.” However, they found that the blood marker for Types A and B were present, but not Type O.

Study co-author Christopher Hübel told New Atlas that Type A is particularly suspicious. “Since previous research has found that proportion of people who are group A is higher in COVID-19 positive individuals, this suggests that blood group A is more likely candidate for follow-up studies," he said.

This raises a lot of questions about your blood type and COVID risk, including what you should do if you happen to have Type A or Type B blood. Here’s what you need to know.

Why might your blood type influence your COVID risk?

This isn’t the first study to find a link between blood type and COVID-19. A paper published in Frontiers in Cellular and Infection Microbiology in November also found that people with Type A (along with Type B) are at a higher risk of getting infected with the virus, while those who have Type O and AB are at a lower risk. And an early study from China also found that people with Type O blood were at a lower risk of being infected with COVID-19, while those with Type A were at a higher risk.

“There have been multiple studies on blood types and COVID risk,” Thomas Russo, M.D., professor and chief of infectious disease at the University at Buffalo in New York. “A few have not supported this association, but the majority have. It’s really fascinating.”

Experts say there is potentially something to this. “Blood proteins may be correlated with immune function and inflammatory response,” says infectious disease expert Amesh A. Adalja, M.D., a senior scholar at the Johns Hopkins Center for Health Security.

Dr. Russo points out that the exact reason for this is still being studied, but there are some theories on why this may happen. One is that having Type O blood gives you antibodies against Types A and AB that may lower your risk of getting infected with SARS-CoV-2, the virus that causes COVID-19, through a particular receptor in your cells. The other is that having A or B blood “enhances the ability of the virus to infect your cells,” he says.

But study co-author Vincent Millischer, Ph.D, a post-doctoral researcher at Karolinska Instituet, stresses that this is all speculation right now. “Even if we showed a causal link between both, we are not able to give an answer on why that might be the case based on our results,” he says.

Does blood type influence how likely you are to get other diseases?

Yup, there’s definitely some precedence here. One study published in 1977 found that people with type O blood were more likely to become infected with cholera bacteria, while people with type A blood were less likely.

Another published in 1993 found that people with type O blood are more likely to become infected with Helicobacter pylori (a stomach infection) than people with A or B blood due to differences in the mucosa in their GI tract. And a 2003 study found that norovirus binds more efficiently to antigens (substances that create an immune response) in people with Type O and A blood, but not as much to those with Type B blood.

A research letter published in 2005 also found a link between healthcare workers with type O blood and a lowered risk of getting infected with SARS-CoV-1, the virus that causes severe acute respiratory syndrome (SARS).

How likely is your blood type to influence your overall COVID risk?

It’s not entirely clear, but experts point out that there are several factors that go into how likely you are to contract COVID-19 and severe COVID. “I don’t think it’s a simple as [having] type A blood,” Dr. Adalja says. “It’s likely multi-factorial.”

Millischer agrees. “While the risk is statistically significant, it is relatively low, which is in alignment with results from previous studies,” he says. Meaning, while your blood type may play a role in your risk of developing severe COVID, it’s not the only or even main factor driving it.

“At the end of the day, age rules in terms of risk—your risk of death goes up with age,” Dr. Russo says. But, he adds, having underlying health issues like lung disease, obesity, or diabetes, plays a role, too.

What should you do if you have Type A or B blood?

Don’t freak out. Regardless of your blood type, the methods of protecting yourself from COVID-19 are the same, Dr. Russo says. That means getting your COVID-19 vaccine and a booster dose, when you’re eligible, wearing a mask when COVID-19 cases are high in your area, and doing your best to practice careful hand hygiene.

Still, if you happen to have Type A or B blood, Dr. Russo says it’s worth reconsidering how you view your risk for severe COVID. “If you have these blood types and you’ve been hesitant to get vaccinated, this may be one more reason why you should do it,” he says.