Does Your Blood Type Increase Your Coronavirus Risk?
Early research hints that your blood type may affect your risk for Covid-19, but experts are quick to caution that these findings should not provide a false sense of security or make you panic.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a new virus, which means that researchers across the globe are trying to learn as much about it as they can as it continues to spread.
As the number of Covid-19 cases rises, certain clear risks have emerged—namely advancing age and a history of underlying heart and lung disease. Researchers are scratching the surface on some others possible factors such as blood type. At least two studies hint that certain blood types may play a role in Covid-19 risk, but infectious disease experts are quick to caution that these studies are preliminary.
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Blood type and risk of Covid-19
There are four major blood groups: A, B, AB, and O, according to the American Red Cross. Individuals with type A blood are slightly more likely to test positive for Covid-19 than those with AB and O blood, finds a study posted in April 2020 on medRxiv.org, a site where researchers can publish studies before the research has been reviewed for publication.
For this study, researchers analyzed the results of 1,559 individuals who were tested for Covid-19 in the New York-Presbyterian Hospital system and whose blood type was known.
Due to the small size of the study, there were not enough individuals with Type B blood groups to draw any conclusions on Type B blood and Covid-19 risk, explains study author Nicholas Tatonetti, PhD, associate professor of biomedical informatics, systems biology, and medicine at Columbia University in New York City. (Here’s the real reason blood is red.)
Other blood-type limitations in the findings
The study’s small size hampered the results in another way—they only looked at Rh positive patients. Blood can also be typed by checking the Rhesus (Rh) factor: This is an inherited protein on the surface of red blood cells, and you either have it—you’re Rh positive—or you don’t (Rh negative). “With respect to Rh blood groups, we report associations only in Rh-positive blood groups,” says Tatonetti; Rh positive is the most common type, so the low numbers of Rh-negative patients prevented drawing any conclusions.
Exactly how, why, or even if blood type truly affects risk for Covid-19 is unclear. “All blood groups are susceptible to infection by SARS-CoV-2, and we saw intubation and death among people of all blood groups,” he says. “Our analysis should not guide individual decision-making, and no one should conclude that their risk is lower or higher on account of their blood group alone.”
Similar Covid-19/blood type findings in China
This study does back up a March 2020 report from Wuhan, China, where the disease began. Researchers compared blood types of 2,173 people diagnosed with Covid-19 to those in the general population. They found that blood group A had a significantly higher risk for Covid-19 compared with non-A blood groups, and blood group O had a significantly lower risk for the virus compared with non-A blood groups. These findings also appear in medRxiv.org.
It’s important to note that both of these studies only looked at the chances of developing Covid-19, not the severity of the infection, adds Matthew G. Heinz, MD, a hospitalist and internist at Tucson Medical Center in Tucson, Arizona, and former director of Provider Outreach in the Office of Intergovernmental and External Affairs, a part of the U.S. Department of Health and Human Services.
A genetic link between blood type and Covid-19 vulnerability
New research strongly hints that infected people with type A blood are much more likely to need oxygen and a ventilator—especially compared to people with type O. This information comes from one of the largest genetic studies of severe Covid-19 to date: Researchers analyzed blood samples from 1,610 patients who needed oxygen or were put on a ventilator and then compared them to 2,205 blood donors without Covid-19. The researchers turned up two genetic variations that left people more vulnerable to the ravages of coronavirus infection—and one of the variations was near the gene that determines ABO blood type.
After comparing Covid-19 outcomes for the groups, the researchers discovered that infected people with type A blood were 50 percent more likely to need oxygen or a ventilator; people with type O were the least likely to experience respiratory failure. (Note that the research isn’t published yet and is still undergoing the peer-review process.)
Blood type may only be an indicator, not a cause
The fact that one of the genome variations is near the gene that encodes for blood type serves to strengthen earlier research linking blood type to Covid-19 risk, says study author Andre Franke, a molecular geneticist at the University of Kiel in Germany. Still, he says, “it may have nothing to do with blood group itself and may be a marker for something else going on at the genetic level.”
For example, both variations are near genes linked to the body’s immune system and could play a role in the “cytokine storm”—a normal immune system response that spins out of control in some patients and begins attacking healthy cells and tissues, leading to severe and even deadly symptoms.
“These are very attractive candidate genes because they regulate the immune system and inflammatory response,” he says. “There is something going on,” he says. “We put our finger on the genetic map and these are the areas we should look at more closely now.”
The next steps are to identify and validate the genes, says Jonathan Sebat, PhD a geneticist at the University of California in San Diego “In addition, [it’s important to] continue the gene discovery so that we can learn more of the biology and … genetic susceptibility of individuals can be quantified somewhat accurately with a genetic test,” he says. “This would be very useful, for example, in clinical trials of new Covid drugs. One can imagine that the effectiveness of a drug might be different in people who have high or low susceptibility to respiratory failure.”
Don’t panic if you’re type A (or feel safer because you’re type O)
It’s way too early to say if blood type plays any role in susceptibility to this virus, says Benjamin Singer, MD, an assistant professor in pulmonary and critical care at Northwestern University Feinberg School of Medicine in Chicago. “It is interesting to measure blood types, but the significance is unclear and outstripped by other risk factors,” he says. “Type O may offer a slight protection and type A may confer a slight increase in risk, but these are small changes against the larger backdrop of other risks such as age and history of underlying disease,” Dr. Singer says.
Don’t let these findings provide a false sense of security or endangerment, he stresses.
Still, your blood type is powerful health information. It may not shed light on Covid-19 risk, but it can tell you more about your chances of developing potentially life-threatening blood clots and heart disease—not to mention your ability to donate blood to those in need. Donations of O negative blood can be used in transfusions for any blood type, the Red Cross points out.
Understanding Covid-19 risks
One of the largest studies to date was published in May 2020 in the journal BMJ. Researchers collected data from more than 20,100 Covid-19 patients admitted to hospitals in England, Wales, and Scotland and found that the average age of patients admitted to the hospital with Covid-19 is 73 years. “Age really outshines every other risk factor that has been identified,” says Dr. Singer.
In addition, more men were admitted to the hospital than women in this report. Although some risk factors can’t be changed—such as gender or blood type—others, such as weight, are modifiable.
Established Covid-19 risk factors
A key finding in this study is that obesity is an emerging risk factor for severe Covid-19 infection. Researchers suspect this is a result of reduced lung function or inflammation that tends to travel with obesity.
Underlying lung and heart disease, diabetes, chronic kidney disease, as well as any conditions that affect your immune system can also increase risk for developing a more serious course of Covid-19, the Centers for Disease Control and Prevention (CDC) reports.
“Obesity, heart disease and diabetes mellitus are chronic diseases that slowly progress and worsen over a period of years to decades, says Adam Spivak, MD, an infectious disease doctor at the University of Utah in Salt Lake City.
Controlling your Covid-19 risk
“Reversing and improving these processes via medications, lifestyle changes and other interventions can help significantly but will typically do so on the same (long) time scale,” Dr. Spivak says.
Still, he adds, “making substantive lifestyle or medical interventions to address these risk factors certainly is a good idea at any time, including now.”
There are things that we know can lower your chances of developing and spreading Covid-19, including washing your hands frequently, wearing a face mask when social distancing isn’t an option, and staying home if you are sick.
- American Red Cross: “Facts About Blood and Blood Types”
- MedRxiv: “Testing the association between blood type and COVID-19 infection, intubation, and death”
- Nicholas Tatonetti, PhD, associate professor of biomedical informatics, systems biology, and medicine at Columbia University in New York City
- MedRxiv: "Relationship between the ABO Blood Group and the COVID-19 Susceptibility"
- Matthew G. Heinz, MD, a hospitalist and internist at Tucson Medical Center in Tucson, Arizona, and Former Director of Provider Outreach in the Office of Intergovernmental and External Affairs, a part of the U.S. Department of Health and Human Services, under the Obama administration
- Andre Franke, a molecular geneticist at the University of Kiel in German
- MedRxiv: “The ABO blood group locus and a chromosome 3 gene cluster associate with SARS-CoV-2 respiratory failure in an Italian-Spanish genome-wide association analysis”
- Jonathan Sebat, PhD a geneticist at the University of California in San Diego
- Benjamin Singer, MD, an assistant professor in pulmonary and critical care at Northwestern University Feinberg School of Medicine in Chicago
- BMJ: "Features of 20 133 UK patients in hospital with covid-19 using the ISARIC WHO Clinical Characterisation Protocol: prospective observational cohort study"
- Centers for Disease Control and Prevention: "People Who Are at Higher Risk for Severe Illness"
- Adam Spivak, MD, an infectious disease doctor at the University of Utah in Salt Lake City