Does blood type affect your risk of severe COVID-19?
New research clashes with study linking type A blood to higher chance of respiratory failure
Mike Moffitt, SFGATE
July 23, 2020 Updated: July 23, 2020 12:27 p.m.
Scientists are trying to determine whether blood type affects the severity of COVID-19 cases. (Photo for illustration purposes.)
If you have type A blood, are you more susceptible to a severe COVID-19 infection?
In June, a medRxiv preprint paper investigating a possible link between COVID-19 and blood types suggested it might.
On the other hand, those with type O blood might be more protected than those with other blood types, according to the study.
The researchers looked at the genetic data of 1,610 COVID-19 patients in Italy and Spain who suffered respiratory failure and needed oxygen or ventilator treatment. Those genes were compared to those of 2,200 uninfected individuals. The scientists identified two gene variants in two regions of the genome associated with a greater likelihood of severe COVID-19 symptoms — including one area that determines blood type.
Patients with type A blood had a 45% increased risk of experiencing respiratory failure after contracting the virus; those with type O had a 35% reduction in risk.
The genome study was reviewed and published by the New England Journal of Medicine on June 17.
An earlier study, not peer-reviewed, by Chinese researchers concluded that type A blood was associated with a higher risk of catching the virus. A total of 38% of COVID-19 patients had type A blood compared to 31% of the healthy population. Patients with type O blood appeared least likely to contract it.
Backing up that analysis was a Columbia University preprint study of 1,559 patients that released similar findings — the odds of testing positive for the coronavirus were higher in individuals with type A blood and lower in those with type O. But the research's other conclusions diverged from the NEJM study. The Columbia researchers found that having type A blood was associated with less risk of being placed on a ventilator. The blood type associated with a greater risk of needing a ventilator was the less common type AB.
Last week, Harvard Medical School researchers based at Massachusetts General Hospital reported in the Annals of Hematology that a person's blood type was not linked to a severe worsening of symptoms in confirmed cases of COVID-19.
"We showed through a multi-institutional study that there is no reason to believe being a certain ABO blood type will lead to increased disease severity, which we defined as requiring intubation or leading to death," senior study author Anahita Dua, HMS assistant professor of surgery at Mass General, told Harvard Medical News.
"This evidence should help put to rest previous reports of a possible association between blood type A and a higher risk for COVID-19 infection and mortality."
For the study, 1,289 symptomatic adult patients who tested positive for COVID-19 had their blood group documented.
The health care publication Advisory Board wrote Wednesday that Joern Bullerdiek, director of the Institute for Medical Genetics at University Medicine Rostock, said the new findings mean "it's probably decided that blood groups are not influencing the outcome of" COVID-19.
In late June, Dr. Ang Li, an assistant professor of hematology and oncology at Baylor College of Medicine, had this to say about the NEJM study:
"I do believe there is likely a connection, and the question is: What does this word 'outcome' mean? The cases are not a study of all COVID patients versus all non-COVID patients, and it's not a study of all severe COVID patients versus all non-severe COVID patients. It's comparing the severe COVID patients versus everyone else without COVID. So, it's hard to know if it's an increased susceptibility to infection or a severity question." (Texas Medical Center/June 29. 2020)
A 2005 study published in JAMA (the Journal of the American Medical Association) found that individuals with type O blood were less susceptible to the "original" SARS virus, SARS-CoV-1.
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Mike Moffitt is an SFGATE Reporter. Email: moffitt@sfgate.com. Twitter: @Mike_at_SFGate
Mike Moffitt
Reporter Mike Moffitt has been writing and editing stories for newspapers and news websites for more than 25 years. Before joining the SFGate team, he worked at the San Francisco Examiner, Arizona Republic and Phoenix Gazette. He covers news, politics, science, sports, outdoors and Bay Area history.