Your blood type does not affect your risk of contracting COVID-19 or developing severe disease, according to a new study by researchers at Intermountain Healthcare that examined outcomes of more than 100,000 patients who were tested for the virus. Early in the COVID-19 pandemic, some studies outside the United States reported that blood type may be a factor in who was afflicted by the virus or who developed severe disease.
However, after studying the blood types of nearly 108,000 patients tested for COVID-19, Intermountain Healthcare researchers found that none of blood types A, B, AB or O had any effect on the susceptibility to the virus or the course of disease.
“We had read a few mostly smaller early studies that indicated patients with type A blood fared worse with COVID-19 and those with type O fared better,” said Jeffrey L. Anderson, cardiologist and researcher at the Intermountain Healthcare Heart Institute in Salt Lake City.
Dr. Anderson said those other studies showed inconsistent results.
“So, instead of studying a few hundred patients, we looked at more than 100,000 patients tested at Intermountain Healthcare facilities, and we found no relationship between a person’s blood type and their susceptibility to COVID-19 or whether they needed hospitalization or ICU care,” he added.
In the study, published this month in JAMA Network Open and to be presented at the American College of Cardiology Scientific Sessions in May, Intermountain researchers identified 107,796 people tested via nasal swab or saliva samples for the SARS-COV-2 virus between March 3, 2020, and November 3, 2020, and who also had a recorded blood type in their electronic health records.
The Intermountain researchers looked at whether those patients tested positive for the SARS-COV-2 virus, whether they required hospitalization for COVID-19, and whether they required ICU care. They found no relationship between any of these outcomes and blood type.
Instead, they found that susceptibility and severity were related to sex (higher risk in men) and race (higher risk in non-white patients), and older age predicted an increased need for hospitalization or ICU care.
“All of these demographic factors are consistent with what we’ve see around the world, which gives us confidence in our database and these results for blood type,” said Dr. Anderson.
An important medical objective during the pandemic is to predict who is most likely to acquire infection and which infected persons are most likely to need hospitalization and intensive care. Identifying these persons in advance can lead to early effective medical interventions and preventive care measures, said Dr. Anderson.
“Blood type was among the factors considered to play a prognostic role earlier in the pandemic, but was not confirmed in this study,” he added.
Potentially tying COVID risk to susceptibility or severity came from studies in China in May 2020 and Italy and Spain in October 2020. Smaller studies in those countries linked type A blood to higher risk of infection or worse outcomes and type O blood to better ones. A larger Danish study, also published in October 2020, implicated disease severity but not susceptibility, and observations from Boston and New York showed no link.
The Intermountain Healthcare study aimed to take a big picture view in a United States population studied prospectively.
Dr. Anderson doesn’t discount the discordant results from some of the other studies entirely though. Blood type profiles and their related phenotypes vary across different populations. Participants in the Intermountain study, who tend to be of Northern European ancestry with some Hispanic/Latinx and other ethnicities, may not have the exact same related phenotypes as people living in China or Southern Europe.
However, doing broad studies to look at the possible link between blood types and disease is important, Dr. Anderson said, and the Intermountain study should be replicated on large scales in other areas of the world and should carefully control for geography, environment, and genetic background.
“These studies can help to better understand any role of blood type in infection and explain whether the apparent discrepancies across studies are due to chance observations or to complex biological effects,” he said. “We looked at a lot of risk factors as to who might need to be hospitalized and who might need more advanced care, and these results show that, for our population at least, blood type is not on that list.”
Other members of the Intermountain research team includes: Heidi T. May, PhD, MSPH; Stacey Knight, PhD, MStat; Tami L. Bair, BS; Joseph B. Muhlestein, MD; Kirk U. Knowlton, MD; and Benjamin D. Horne, PhD, MStat, MPH
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