Blood type, among other genetic factors, could be indicators of why certain groups of people are more susceptible to contracting COVID-19 and developing severe symptoms.
This is according to a study published on 17 June by The New England Journal of Medicine where European researchers sought to shed light on the role genetics play in the disease, aside from factors such as age, and those with pre-existing medical conditions.
Relationship between Blood Type and COVID-19
More than 1,900 severely infected COVID-19 patients were compared with over 2,000 of those who were healthy or experienced mild to no symptoms in Spain, Italy, Denmark, Germany and other countries.
Results from the genetic analysis confirmed a potential link between variations of the ABO blood-group system.
It also confirms a previous report from China that suggested a link between blood types and the way COVID-19 affects individuals—one which many discounted due to it being a “crude study.”
Higher Risk in Blood Type A Than in Other Blood Groups
There are said to be 4 main blood types, A, B, AB and O.
Findings suggest that those with Blood type A are more vulnerable to risks of severe COVID-19 infections—facing a 45% higher risk—as compared to people with other blood types.
People of Blood type O, on the other hand, were said to face 35% lower risks.
“A cluster of variants in genes” were said to be more commonly found in patients with severe COVID-19, influencing immune responses.
Coronaviruses are able to leverage on ACE2—a cell-surface protein—associated with these genes, to enter and infect cells in the body.
Protective Effect in Blood Group O
According to the study, people with type O blood have the ability to recognise certain proteins as foreign—even those on virus surfaces—therefore making people with Blood type O less likely to contract coronavirus.
This is also in line with research conducted by genetic testing giant 23andMe where preliminary results from over 750,000 participants suggest type O blood being especially protective against Sars-CoV-2, the virus that causes COVID-19.
Individuals with type O blood are between 9% and 18% less likely to have tested positive for coronavirus, as compared to those of other blood types.
And this extends beyond just the coronavirus on the protective qualities individuals with Blood type O have, according to Hari.
“A genetic cousin of the coronavirus causing the current pandemic” was also evident during the SARS outbreak. He noted that those with Blood type O were “less likely to get the severe disease”.
Scientists Urge Caution
Still, the New England Journal of Medicine does not firmly prove the connection between blood type and how COVID-19 affects individuals.
More verification from patients are still required, and pooling in of resources from various groups.
The evidence of a role for blood type is “tentative … it isn’t enough of a signal to be sure,” said Dr Eric Topol, head of the Scripps Research Translational Institute in San Diego, to CBS News.
It, however, allows for scientists to further bank on research to help identify and protect more at-risk groups, as well as paving the way to speed up treatments and drug development.
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