SALT LAKE CITY – Your blood type doesn’t factor in your risk of contracting COVID-19 or developing a serious case of it, researchers at Intermountain Healthcare and other institutions have determined.
Their findings, published earlier this month in the Journal of American Medical Association, counterbalance previous global studies and studies suggesting that blood type was a factor in why some people were more likely to experience symptoms of COVID-19 than others.
“I think it’s important because it has really been one of our primary goals for us to identify patients at higher risk and build risk scores,” says Dr. Jeffrey Anderson, a cardiologist and investigator at the Intermountain Medical Center Heart Institute, and the lead investigator on the study.
Hospitals use a variety of possible risks to determine whether or not to hospitalize a person, or what other care they should receive. The results of the study indicate that ABO blood group is not a factor necessary to evaluate risk.
Anderson explained that the research was prompted by the many unknowns within COVID-19. Medical professionals around the world had little to no answers as to why some people got sicker than others. If they could solve the puzzle, they could contribute to better treatment of patients.
The data pointed to older people, as well as those with high obesity, diabetes, high blood pressure, and pre-existing lung or heart disease. But since COVID-19 ravaged China and Europe before the US, global researchers got a head start on other potential factors.
A study that emerged in China early last year piqued Anderson’s interest. It suggested that blood type played a role in contracting COVID-19. More specifically, it suggested that people with blood group A had a higher risk of contracting COVID-19 and that blood group O had a lower risk of getting infected.
Researchers in Italy and Spain then released a study that suggested that blood type was not a factor in contracting COVID-19, but it did take into account the severity of a new case. In a somewhat similar result, the study suggested that blood group A resulted in more severe cases and type O resulted in less severe cases. It is unclear how many medical professionals relied on these studies when dealing with COVID-19 treatment.
“We started to get interested in this and wondered if we should look into this too, especially as other reports came out with variable results,” Anderson said. “There was one from Denmark who said it was contagious, but not the severity of the disease affected, and then here from the US from New York and Boston … where there was no risk association.”
So researchers from Intermountain Healthcare, the University of Utah School of Medicine and Stanford University tried to confirm the findings of the earliest studies.
They examined the results of 107,796 people tested for COVID-19 in Utah, Idaho, and Nevada between March 3, 2020 and November 2, 2020. Anderson said the healthcare database provided a goldmine for researchers because it provided them with the patients’ COVID-19 test results and their blood groups. It also provided information on how serious a case became if someone was hospitalized.
According to the data, about 10.6% of the nearly 108,000 people involved in the study tested positive for COVID-19. Broken down by blood type, researchers found that the percentage of people who tested positive for COVID-19 essentially matched the percentage who tested negative.
For example, blood group A accounted for 39.6% of the positive results, but also 40.4% of the negative results. Type B represented 9% positive and 9.3% negative. Type AB accounted for 3.2% positive and 3.3% negative, while type O accounted for 48.1% positive and 47.1% negative.
“There was no association between ABO type and the risk of getting infected,” Anderson said.
Similar patterns emerged in hospital admissions and intensive care unit cases. Of the 11,468 positive cases, 2,326 ended up in hospital; and 706 of those hospitalized ended up in the ICU.
Again, blood group accounted for 38.6% of hospital admissions and 39.9% of non-admitted cases. It accounted for 36.4% of the IC stays and 39.5% of the non-IC hospital admissions.
Type B accounted for 8.8% of hospital admissions and 9.1% of non-hospital admissions, as well as 8.6% of ICU cases and 8.9% of non-ICU cases. Type AB represented 3.4% of hospital admissions and 3.1% of cases not requiring hospitalization; it accounted for 2.8% of the ICU cases and 3.6% of the cases where the IC unit was not required.
Finally, 49.2% of the hospital admissions involved persons with type O blood compared to 47.9% of the cases where no hospitalization was required; it also accounted for 52.1% of all ICU cases in the data, compared with 48% of no hospitalization.
The results came as somewhat of a surprise to researchers, especially as studies over the years have found links between type A blood and heart attack risk, Anderson said.
“We entered into this study thinking that we would probably validate or verify the reports of a relationship, but we found none,” he said.
That is not to say that the research did not find other connections. The data confirmed theories that the elderly, men, and people in minority communities were at higher risk of contracting or developing serious illness from COVID-19.
I think it is extremely important that we learn everything about this virus so that we can best fight it.
–Dr. Jeffrey Anderson, cardiologist and researcher at the Intermountain Medical Center Heart Institute
Anderson added that it is also possible that the findings are regional. There is a possibility that other factors have caused other regions around the world to achieve different results.
“Blood type varies in terms of frequency among different populations and so on,” he said. “There may be several associations with blood group that explain some of the other results, and the results differ from other areas.
“In other words, blood types can be associated with other characteristics that cause disease or put people at risk,” he continued. “This is called an association, which is different from what we would call a risk factor that is causal.”
For researchers like Anderson, finding no relationship between blood type and COVID-19 risks is a lot closer to solving the COVID-19 puzzle.
It adds to the growing list of items learned since SARS-CoV-2 and COVID-19 were first identified in late 2019. Since SARS-CoV-2 was a new coronavirus, this meant medical experts started the same knowledge as everyone else about how it spreads and how it affects people.
“I think it is extremely important that we learn everything about this virus so that we can best fight it,” said Anderson. “We’re not done yet. It’s great to see the light at the end of the tunnel, to see our numbers come down, but this will still be with us at some level for, I think, the coming many months and maybe years.
“The more we can learn about it, the better off we are.”