A person’s blood group does not affect their risk of developing severe Covid-19 or being hospitalised by the infection, a study has found.
Previous studies have indicated that people with type A blood are more at risk of catching the coronavirus.
To determine if this was true, US doctors analysed health records of more than 100,000 people who had a Covid-19 test across Utah, Idaho, and Nevada between March and November 2020.
Cross-referencing their Covid status with blood group revealed there to be no association between the two, debunking the previous findings.
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People are more at risk of catching the coronavirus if they have type A blood, a study has found. Lab-based analysis investigated previous reports that blood group impacts on an individual’s susceptibility to infection with SARS-CoV-2
Blood group is a trait which is determined by a person’s DNA and depends on the versions of genes inherited from a person’s parents.
These genes dictate the presence of antigens on the surface of red blood cells, the donut-shaped vessels which carry oxygen around the body in arteries and veins.
Antigens are protruding proteins and there are two versions, A and B, which are found on the surface of red blood cells, also known as erythrocytes.
Every person has either A, B, A and B, or none. These people will therefore have blood type A, B, AB and O, respectively, and this is known as the ABO blood group system.
Another antigen on the cells, called Rhesus, is either positive or negative and this determines if a person is, for example, A positive or A negative.
Blood groups vary in their commonality depending on geography and ethnicity but in the UK, the most common group is O positive, followed by A positive.
Previous studies had found that people with type A blood are at greater risk of catching the virus.
The coronavirus SARS-CoV-2 has a higher affinity for other cells — such as those found in the respiratory tract — which express a type A-specific molecule called an antigen
One study hinted that type A people have more receptors which the virus can bind to, making them more susceptible.
But Dr Jeffrey Anderson, of the Intermountain Medical Center Heart Institute in Salt Lake City, performed the most comprehensive and controlled analysis yet.
‘With contrasting reports from China, Europe, Boston, New York, and elsewhere, we embarked on a large, prospective case-control study that included more than 11,000 individuals who were newly infected with SARS-CoV-2, and we found no ABO associations with either disease susceptibility or severity,’ the authors of the study write in their paper, published today in JAMA Network Open.
‘Given the large and prospective nature of our study and its strongly null results, we believe that important associations of SARS-CoV-2 and Covid-19 with ABO groups are unlikely,’ they add.
The researchers can not explain why the previous studies came to different conclusions, but cite various factors which may have led to the previous results.
They say pure chance, publication bias, genetic differences, geography and variants may have led to skewed data indicating that some blood groups are more at-risk.
However, the study did find that although blood group does not, other factors do indeed increase the risk of Covid-19.
These included being a man, being older and also people not of white ethnicity.
‘Among individuals with Covid-19, hospitalisation was associated with male sex and age,’ the researchers write. ‘Admission to an ICU was also associated with male sex and age.’
The data also found that non-white people, including African Americans; American Indians or Alaskan Natives; Native Hawaiian or Pacific Islanders; Asians; and people who did not disclose their ethnicity are more likely to test positive.
However, there was no link between these people and disease severity.
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