So far, age, gender, and comorbidities have been viewed as determinants of COVID-19 disease progression. Now, an unexpected factor seems to be influencing susceptibility to COVID-19, according to two recent studies: blood type.

In both studies, published last week in Blood Advances, researchers said people with blood type O might be less prone to the disease than people with other blood types.

Although the outcome of the two researches was the same, there were some notable differences. The Danish study found that more COVID-19 positive people had blood types A, B and AB, while fewer people with blood type O tested positive for the coronavirus infection.

On the other hand, the Canadian study showed that in addition to blood group O, blood group B also seemed to offer a certain immunity to the novel coronavirus and its complications. According to the study, more people had to be treated with types A and AB, especially when compared to blood types O or B. More people in the former category were also treated in intensive care units with ventilators for possible lung damage and dialysis because of kidney dysfunction.

Nevertheless, the authors felt that further research was necessary to establish a cause-effect relationship between blood group and susceptibility. More importantly, previous studies published earlier this year found that belonging to a particular blood type does not mean that one should be less careful with COVID-19 or be warned about relaxing vigilance.

Danish research

Both the Danish and Canadian studies compared people with COVID-19 to control groups – which always gives a study accuracy. The studies compared cases with national registries of people without COVID-19 in their respective countries, including their blood types.

In the Danish study, 7,422 people who tested positive between February 27 and July 30, 2020 were weighed against 38% of the Danish population who had not tested for SARS-CoV-2 infection. “Much less among the SARS-CoV-2 people [blood] Group O individuals were found; Conversely, more A, B and AB individuals were found. When blood type O was excluded, no significant difference was found between A, B and AB, ”the paper explained.

According to the Denmark-based researchers, blood types were not a risk factor in assessing hospital stays and deaths from COVID-19. Similarly, age, co-morbidities, and inactivity in the health sector did not explain the benefit enjoyed by those with blood group O, making this correlation a medical mystery for now.

“Our results of similar relative protection by blood group O in young people, the healthcare sector, and those with no registered cardiovascular diagnosis suggest that associations between non-O blood types and comorbidities do not explain the apparent protection of those in group O,” the said Newspaper.

From now on, more research can shed some light on why this is happening.

The Canadian paper

The study, based in Vancouver, Canada, analyzed 125 patients admitted to intensive care from March 1 to April 28, 2020 at six hospitals in Vancouver. Of these patients, 95 had the required information about their blood types. In order to identify contrasting factors, these participants were divided into two groups: those with blood group O or B and others with blood group A or AB.

The results of the study are:

  • People with blood groups A and AB needed more medical help.
  • About 84% of the blood groups A and AB needed a ventilator to breathe. For people with blood groups O and B, 61% needed the same thing.
  • Among A and AB patients, about 32% needed dialysis, a treatment that helps kidney function when the kidneys fail. Not that many patients with blood groups O and B needed dialysis.

“The unique part of our study is our focus on blood type severity on COVID-19. We have observed this lung and kidney damage and will look to investigate the effect of blood type and COVID-19 on other vital organs in future studies,” said Dr . Mypinder S. Sekhon of the University of British Columbia in a press release.

On the contrary, another study published in the Annals of Hematology in July said that the severity of the disease could not be predicted by blood types. “We have shown through a multi-institutional study that there is no reason to assume that a certain ABO blood group leads to an increased severity of the disease, which we define as requiring intubation or death,” said Anahita Dua, assistant professor for surgery in Massachusetts General Hospital and senior author, said in a news release.

Seema Prasad is a freelance health reporter based in Bengaluru, India. She tweeted @SeemaPrasad_me

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