New research: No link between COVID-19 and blood type

Study looked at thousands of COVID-positive patients

BOSTON — When COVID-19 hit last year, it left doctors reeling.

“We suddenly had this disease upon us, taking our patients, hurting our patients,” said Dr. Anahita Dua, a vascular surgeon at Massachusetts General Hospital. “And we didn’t know our enemy.”

One thing doctors needed especially to figure out: why some got deathly ill from COVID-19 infections, while others had no symptoms at all.

That led to the good-faith effort by researchers and clinicians around the world to share what seemed any pertinent information about the virus, even if, at times, the knowledge consisted of anecdotal evidence rushed to market.

“I think that’s what led to a lot of scientific research being put on the Internet to be shared globally because this was a global pandemic,” Dua said. “But what the risk was, and what we lost in doing that, is our scientific process to some extent.”

It is a process that normally requires peer review of submitted papers, Dua said.

“The different peer review groups will review and have a critique, then you answer and it’s a process to get something published. It’s really vetted,” she said.

Less vigorously reviewed last year, research out of China that appeared to show a correlation between blood type and susceptibility to COVID-19, specifically, that those with Blood Type A, were more susceptible to COVID-19 infections than those with Blood Type O.

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Subsequent research from Europe looked at the severity of COVID-19 infection and blood type. Again, Blood Type A was found to have more severe infections than Blood Type O. These were, however, observational studies, that is, they were not set up in a scientific manner because that would require actually infecting both blood types with COVID-19 to see what happened.

“And sometimes observations are observations,” Dua said, “Not really scientific fact. And we had to be very careful walking that line. And we saw mistakes that were made, as we know.”

Dua and other researchers at MGH looked last year at the connection between blood type and COVID-19 severity and found no association after examining the records of some 1,300 patients in five Boston hospitals.

And now, new research out of the University of Utah Medical School, and published in JAMA Network Open, would seem to not only validate Mass General’s conclusion but to take the question one step further by also finding no link between susceptibility to COVID-19 infection and blood type.

In fact, after reviewing medical records from thousands of COVID-19 patients in three states, the researchers actually found more positive tests in the Type O group than the Type A.

“I think one of the challenges that this study articulates quite nicely is when you look at studies that came out of China or Europe or now in the U.S., there’s been conflicting results,” said Dr. Sean Stowell, a pathologist at Brigham and Women’s Hospital, who is also researching the topic.

In laboratory studies, Stowell said they have found some evidence the virus has an affinity for one blood antigen over another.

“What we found is that the virus actually does bind to Blood Group A better than some of the other Blood Group antigens, suggesting that there may be an association between some of the findings that have been reported, that people who have Blood Group A might be slightly more likely to get infected than people who are, say, Blood Group O,” Stowell said.

But lab studies are not a substitute for human studies, Stowell cautioned. And any differences between the virus and blood types, he thinks, is likely to be subtle.

“More research is definitely warranted,” Dua said. “Stronger studies are warranted. But right now, if you look at all the literature that’s out there, it does seem to sway towards the fact that blood type does not seem to have an impact.”

Dua said the Utah study is important because it allows clinicians to concentrate on the things that really do matter when it comes to assessing the risk of COVID-19 infection.

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