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.
Cross-referencing their Covid status with blood group revealed there to be no association between the two, debunking the previous findings.
Scroll down for video
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
Breakdown of British people by blood type
• O positive: 35%
• O negative: 13%
• A positive: 30%
• A negative: 8%
• B positive: 8%
• B negative: 2%
• AB positive: 2%
• AB negative: 1%
Source: 900,000 blood donors on the NHS blood and transplant register
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.
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
Trial finds convalescent plasma therapy DOESN’T cut the risk from Covid-19
Injecting coronavirus patients with the blood of survivors does not boost their chances of getting better, a major study has found.
Scientists running the REMAP-CAP trial have stopped enrolling infected ICU patients after finding ‘no evidence’ convalescent plasma therapy boosted survival rates.
The therapy has also been dropped by the world-leading RECOVERY trial.
The former focuses on critically-ill patients while the latter involves hospitalised, but not critically ill individuals.
The findings from the study trials sounds the death knell for the once promising treatment which was being touted by the NHS, NIH and academics.
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.
Previous evidence of how blood type affects Covid
On March 17 2020, just as the virus was taking hold in the UK and before the first lockdown was introduced, MailOnline reported that Chinese researchers found people with Type A blood are significantly more likely to catch coronavirus than those with Type O.
The study in Wuhan also found those with Type A blood are more likely to die from COVID-19.
In the general population Type O blood (34%) is more common than A (32%).
However, among COVID-19 patients, people with Type O accounted for just 25%, whereas Type A made up 41%.
People with Type O blood made up a quarter (25 per cent) of deaths in the research. Normally, Type O people make up 32 per cent of people in Wuhan.
Researchers in China assessed 2,173 people who had been diagnosed with the coronavirus, including 206 people who died after contracting the virus, from three hospitals in Hubei.
Academics compared the data of the infected Wuhan patients with 3,694 non-infected people in the same region.
Of the 206 patients in the study who died, 85 had type A blood, equivalent to 41 per cent of all deaths.
In the healthy Wuhan population, a city of 11 million people, 34 per cent of people are type A.
In the study cohort, 52 of the people who died were type O, making up a quarter of all deaths. Under normal conditions just 32 per cent of people are type O.
The figures for all infections, not just deaths, are 26 per cent and 38 per cent for type O and type A, respectively.
In November 2020, MailOnline again reported on a similar study which found people with type A blood are more at risk.
Researchers from the Institute for Clinical Evaluative Sciences in Toronto studied 225,556 people who had a blood test between 2007 and 2019 and a Covid swab in 2020.
It found people with a type O blood are 12 per cent less likely to catch the coronavirus than other blood types, a study has found.
It also revealed that those with a negative blood type (O-, A-, B- or AB-) are, on average, 21 per cent less likely to get the virus than people with a positive type.
Individuals with type O or negative blood are also 13 per cent and 19 per cent less likely to develop severe symptoms or die, respectively.
In the UK, around 15 per cent of the population have a negative blood type and almost half (around 48 per cent) are type O.
Around one in eight people (13 per cent) are O-, which are 26 per cent less likely to get infected and 28 per cent less likely to develop severe symptoms or die.