Can Your Blood Type Affect COVID-19 Risks?

Over the years since COVID-19 first emerged, people have wondered if blood type plays a role in the body’s ability to protect against COVID infection. After all, why is it that some people are worse affected by COVID than others? Does it come down to genetics? 

There are four main blood types: A, B, AB, and O. Blood types can be further classified by a protein called the “Rh factor.” This is either present (+) or absent (-). So there are eight different blood types: 

1. A+

2. A-

3. B+

4. B-

5. O+

6. O-

7. AB+

8. AB-

Your blood type is genetically determined, meaning you inherit it from your parents.

Knowing your blood type is important for several reasons, like if you need a blood transfusion. Different blood types are also linked to certain health conditions, like heart attacks and blood clots. And evidence is emerging that links certain blood types to a higher risk of getting COVID, having severe symptoms, and a higher risk of certain long-term complications from COVID.

Is there a link between blood type and COVID risk?

It seems so. Over the past several years, researchers have tried to answer this question using the available data. Early in the pandemic, researchers noticed that people with blood Type A seemed to be more likely to get sick with COVID. And people with blood Type O seemed to be less likely to get it. On the other hand, some studies found no connection at all. 

Blood type and the risk of getting COVID

Here are some of the highlights over the past few years:

• U.S. study of 107,796 people: This study didn’t find any relationship between blood type and COVID risk or disease severity.

• Canadian study of 398,671 people critically ill with COVID: People with Type A or AB had a higher risk of needing a ventilator and having a longer stay in the intensive care unit, compared to people with Type O and B. 

• Chinese study of 2,173 people: People with Type A blood had an increased risk of getting infected with COVID. And people with Type O had a lower risk. 

• French study of 1,279 military members: This study didn’t find a relationship between blood type and the risk of COVID infection.

• U.S. study of 14,112 people: This study found a slightly higher risk of infection among all blood types, except in people with Type O. People with Type A had a lower risk of needing intubation, and people with Type AB and B had an increased risk. The risk of death increased for people with Type AB and decreased for people with Type A and B.

• Lab research out of Brigham and Women’s Hospital, Harvard Medical School: This research showed that the virus that causes COVID is better at infecting people with Type A blood, compared to Type O. Researchers found that having Type A blood was linked with a 25% to 50% increased risk of getting COVID. The increase depended on the variant involved — with the omicron variant being the worst culprit. This seems to be because it’s physically harder for the virus that causes COVID to enter the cells of people who have Type O blood.

Now, there’s also evidence that COVID affects people with non-Type O blood worse in the long-term than people with Type O.

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In an analysis of UK Biobank health data, researchers compared 10,000 adults who tested positive for COVID-19 before the end of 2020 (before vaccination became available). They compared these people against more than 200,000 adults who hadn’t been infected with COVID during the same period. They collected data on both groups for almost 3 years, until October 2022. 

Like other research in this space, they also found that people who tested positive for COVID were more likely to be blood Type A, B, or AB. They didn’t see a link between blood type and risk of hospitalization for severe COVID. 

Blood type and the risk of heart attacks and stroke after COVID

Researchers found something else too: People with non-O blood types (A, B, or AB) had a 65% higher risk of heart attack and stroke after a hospitalization for COVID compared to those with Type O blood. 

Again, this research was based purely on people who were infected with COVID in 2020, before vaccination was available. It’s not clear how this information applies to people who were infected with later strains of COVID — or after vaccination.

RH-negative blood and COVID

There might be a link between the Rh factor and COVID. But so far, only a few research studies have looked at this topic and haven’t found anything conclusive. 

In a 2020 study of over 14,000 people, researchers found that people with Rh-negative blood type had a decreased risk of COVID infection as well as of intubation and death. 

Another study from 2021 that looked at over 225,000 people also found that people who were Rh-negative had a slightly lower risk of getting infected with COVID. This was especially the case if they were blood Type O. The people who were Rh-negative who did get COVID infection were also less likely to get very sick or die from it compared with people who were Rh-positive. 

But a 2022 meta-analysis didn’t find an association between Rh-factor and COVID infection. More studies are needed before we can say for sure whether there’s a connection.

EXPERT PICKS: WHAT TO READ NEXT

• What does your blood type mean for your health? There are eight different blood types. Yours is genetically determined. Here’s why it’s important to know what blood type you are. 

• COVID-19, blood type, and heart attacks and stroke: People who got the original strain of COVID have a higher long-term risk of heart attack and stroke. That risk may be higher for non-O blood types. 

• Need to update your COVID vaccine? Here’s what you need to know about the latest COVID vaccines available to you. 

Can being blood Type O protect you from COVID?

It seems so. Some studies have concluded that people with blood Type O may be less likely to get COVID. But more research is needed. 

In a 2020 study of nearly half a million people, those with blood Type O had a lower risk of getting infected with the virus that causes COVID. 

A 2022 meta-analysis of 22 different studies also found that people with blood Types A, B, and AB had a higher risk of getting COVID infection compared to blood Type O. The authors of this meta-analysis concluded that blood Type O seemed to be protective against COVID infection. 

And the 2024 analysis of the UK Biobank data (mentioned above) found a similar link: 

• People with blood Type O were less likely to have tested positive for COVID during the first wave. 

• And they also had a lower risk of cardiovascular complications from COVID. 

All the same, having blood Type O doesn’t make you immune to the virus that causes COVID. People with Type O blood can still get COVID. And they can still pass it to other people. 

Does your blood type affect COVID vaccine side effects?

No. So far, there’s no clear connection between blood types and side effects from COVID vaccines. One study of over 3,000 people who got a COVID vaccine found no difference in side effects or other issues between people with different blood types.

Vaccines are safe and effective at lowering the risk of getting sick and dying from COVID infection. The CDC recommends COVID vaccines for all people in the U.S. over the age of 6 months, regardless of blood type (unless you’re allergic to the vaccine). 

What’s the best and worst blood type to have when it comes to COVID risk?

It’s not clear. Experts just don’t know enough to say for sure. It’s not clear whether all people (or just some people) with blood Type A have a higher risk for COVID. And the same goes for blood Type O. 

After all, your risk of getting sick with COVID depends on many different things — not just your blood type. Blood type is one small piece of a much larger puzzle. Your overall health, age, and even your race can all play a role in how sick you may get from COVID. And there may be other factors scientists haven’t discovered yet. 

No matter what your blood type is, you should still get vaccinated and do what you can to protect yourself from getting COVID infection. There’s no blood type that’s a “guarantee” against getting sick from the virus that causes COVID. 

Who’s most at risk of COVID infection?

The science is clear that some people have a higher risk of being very ill with COVID infection. This includes people who: 

• Are age 50 and older: Compared with younger people, older adults are more likely to end up very sick if they get COVID. They’re also more likely to be hospitalized for COVID treatment and are more likely to have serious complications (including death). 

• Are immunocompromised: Your immune system needs to be strong to fight off any infection, including COVID. Some medical conditions and treatments reduce the ability of your immune system to work and increase your risk of getting very sick with COVID. 

• Have other health conditions: People who have certain health conditions, like asthma, cancer, chronic obstructive pulmonary disease (COPD), diabetes, dementia, kidney disease, liver disease, and a history of stroke may have a higher risk for severe COVID illness. 

• Have a disability: People with certain disabilities may be more likely to get very sick from COVID, especially if they have other medical problems, live in shared housing, or face unfair treatment in their communities. 

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Written by:

Alina Goldenberg, MD, MAS, FAAD

Alina Goldenberg, MD, MAS, FAAD, is a board-certified dermatologist in private practice. She is also an assistant clinical professor in the Department of Internal Medicine at the University of California, Riverside School of Medicine.

Edited by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. A pulmonologist and hospitalist, she practiced and taught clinical medicine at hospitals in London for a decade before entering a career in health education and technology.

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