Study refutes the theory that blood type affects COVID risk

A or B, AB or O, it doesn’t matter – your blood type has nothing to do with the risk of getting serious COVID-19, a new study concludes.

At the beginning of the pandemic, some reports suggested that people with type A blood were more susceptible to COVID, while those with type O blood were less.

But an analysis of nearly 108,000 patients in a three-state health network found no link between blood type and COVID risk.

“Since the beginning of this pandemic, there have been postulated associations between blood type and disease susceptibility,” said Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Safety.

“From this large study, it appears that there is no association between blood type and susceptibility or severity, and other explanations were probably present,” added Adalja, who was not involved in the study.

A previous report from China suggested that blood type may influence the risk of COVID. Subsequent studies from Italy and Spain confirmed this, the researchers said in background notes.

However, other studies from Denmark and the United States have offered mixed and conflicting results.

To clarify things, researchers led by Dr. Jeffrey Anderson of the Intermountain Medical Center Heart Institute in Murray, Utah, analyzed data from tens of thousands of patients at Intermountain Healthcare, a nonprofit health care system in 24 hospitals and 215 clinics across Utah, Idaho and Nevada.

Of those in the analysis, almost 11,500 tested positive for coronavirus, while the rest tested negative.

Blood type does not play a significant role in the risk of contracting COVID, the researchers reported on April 5 in Open JAMA network.

“I have always said that this whole blood type thing is very fuss about nothing,” said Dr. Aaron Glatt, head of the department of medicine and hospital epidemiologist at Mount Sinai South Nassau in Oceanside, NY. “It was never significant enough that people would be terrified if they had one blood type or reassured if they had another blood type. That never made any practical difference.”

Glatt was not involved in the new research.

He said the findings of previous studies demonstrate why correlation is not the same as causation – in other words, why showing that two things are statistically linked is not the same as proving that one caused the other.

“If you go and look at enough things, you will find some random findings that may or may not have any meaning,” said Glatt. “Some people looked at so many different variables and one of them was the blood type. They saw that some people did worse with a certain blood type, but the studies were conflicting, which makes sense if it’s random.”

Glatt concluded: “It calms everything down, but it should never have happened.”

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