Almost half of Britons could be less likely to catch Covid-19 because they have Type O blood

People with blood type O could be less likely to get sick with Covid-19, according to new research.

Their risk of severe complications such as organ failure — and even death — is also reduced, say scientists.   

Danish researchers used data from 473,000 individuals tested for Covid-19 against a control group of more than 2.2million people from the general population. 

Among those who tested positive for the virus, they found fewer people with blood type O and more people with A, B, and AB types.  

Results from a second study also suggested individuals with blood types A and AB, who collectively make up just under 45 per cent of the UK and US populations, are at higher risk of having severe symptoms and complications — such as the need to be ventilated — than than those with type O or B.

The findings build on a growing body of research suggesting a link between blood type and coronavirus risk, as well as the apparent protective effect of blood type O. Around half of people in the UK and US have type O blood. 

People with severe coronavirus and genes that code for Type A blood were 50% more likely to need oxygen or ventilator support, compared to those with other blood types (stock image of the coronavirus in the blood)

Lead author of the first study, Dr Torben Barington, of Odense University Hospital, said: ‘It is very important to consider the proper control group because blood type prevalence may vary considerably in different ethnic groups and different countries.’

His team tested 196,252 people with blood type O and 277,402 with types A, B, or AB.

Whilst 38 per cent of people who tested positive for Covid-19 had type O blood, 62 per cent had type A, B or AB blood. 

The majority of people in the latter group (202,507) had type A blood, with far fewer having type B (53,735) or AB (21,160). 

Rates of infection in these last three groups were similar at around 1.6 per cent, compared to 1.4 per cent for those with blood type O. 

The trends remained the same after the researchers took into account ethnicity, which affects blood group distributions. 

What have some of the studies into blood type and Covid-19 shown?

When? March

By who? Chinese scientists from multiple institutions

What did scientists study? 

2,173 people who had been diagnosed with coronavirus, including 205 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.   

What did they find?  

That people with type A blood are significantly more likely to catch coronavirus than those with Type O blood. 

They also found that people with type A blood are more likely to die from Covid-19.   

What were the study’s limitations? 

The researchers pointed out that a larger study group would make the figures more reliable. 

The findings did also not explain the mechanisms that show whether a person with blood type A is more susceptible to the Covid-19 disease.      

When? June

By Who? Genetic testing company 23AndMe, based in the US

What did scientists study? 

750,000 participants, including 10,000 people who reported having Covid-19. 

Researchers identified a variant in the ABO gene, responsible for difference blood types, that was associated with a lower risk. 

What did they find? That having a certain blood type may help protect you against coronavirus.

People with type O blood were up to 18 per cent less likely to test positive for Covid-19. 

About 1.3 percent of 23andMe research participants with type O blood tested positive for COVID-19.

By comparison, 1.4 percent of those with type A blood and 1.5 percent of people with type B or type AB blood were confirmed to have the virus.

What were the study’s limitations?   

At the time of publication, the findings had not been peer reviewed or published in a medical journal.    

When? June

By Who? Scientists in Italy, Spain, Denmark, Germany and other countries 

What did scientists study? Analysed the genetics of Covid-19 patients. 

They compared about 2,000 patients with severe COVID-19 to several thousand other people who were healthy or who had only mild or no symptoms.

Researchers tied variations in six genes to the likelihood of severe disease, including some that could have a role in how vulnerable people are to the virus. They also tied blood groups to possible risk.

What did they find? Those who had Type A blood were more likely to have severe disease while those with Type O were less likely.  

What were the study’s limitations? 

 A small sample size and the urging of caution by other scientists.

One, Dr Eric Topol, head of the Scripps Research Translational Institute in San Diego, said the evidence of a role for blood type is ‘tentative…it isn’t enough of a signal to be sure.’     

When? June

By Who? University of Kiel in Germany

What did scientists study? 

DNA samples from Italian and Spanish patients who went into respiratory failure after contracting coronavirus.

They sequenced the genomes of 1,610 patients from seven hard-hit cities in the two countries.

They searched for patterns in these genomes, common themes in the genetic variation that might point a DNA basis for the predisposition of these patients to fall life-threateningly ill.

By comparing these genomes to those of 2,205 people who did not become severely ill, the researchers homed in on two points along the genome.

The more notable of the two gene areas they identified was one that codes for people’s blood types.

What did they find? 

The gene variant that underlies Type A blood was much more common among severely ill COVID-19 patients.

People who had Type A blood were 50 percent more likely to be so sick they needed oxygen support or even to be put on a ventilator.

Type O blood, on the other hand, was linked to a lower probability of severe illness.

What were the study’s limitations?  

 Small sample size.

Researchers still don’t know for sure what about this gene variant that leads to Type A blood would make someone more susceptible to coronavirus. 

A slightly higher proportion of black people (51 per cent) have type O blood than in the white population. 

The authors concluded that ‘blood group O is significantly associated with reduced susceptibility to SARS-CoV-2 infection’.

A second study of 95 critically ill Covid-19 patients in hospital in Vancouver found the A and AB blood types were at higher risk of severe symptoms than those with O or B.

They were more likely to require mechanical ventilation, suggesting they had greater rates of lung injury from the virus, and dialysis for kidney failure.

Whilst 61 per cent of people with blood types O or B needed to be mechanically ventilated, 84 per cent of people with blood types A or AB needed the life-saving treatment.  

It suggests these two blood groups have an increased risk of organ dysfunction or failure due to Covid-19.

What’s more, while people with blood types A and AB did not have longer overall hospital stays, those who were admitted to intensive care spent longer in the units than people with other blood groups.

This may also signal a greater Covid-19 severity level, said the Canadian team.

Lead author Dr Mypinder Sekhon, of the University of British Columbia, said: ‘The unique part of our study is our focus on the severity effect of blood type on Covid-19.

‘We observed this lung and kidney damage, and in future studies, we will want to tease out the effect of blood group and Covid-19 on other vital organs.

‘Of particular importance as we continue to traverse the pandemic, we now have a wide range of survivors who are exiting the acute part of Covid-19, but we need to explore mechanisms by which to risk stratify those with longer-term effects.’ 

As the pandemic continues, the global biomedical research community is working urgently to identify risk factors and potential therapeutic targets.

The potential role of blood type in predicting infection has emerged as an important scientific question.

The papers, published in the journal Blood Advances, add to evidence of a link.

There are four main blood groups — A, B, AB and O.  

The difference in blood groups depends on attachments to red blood cells called antigens. 

The presence, or absence, of these molecules dictates what blood type a person is.

Antigens may let the virus into the body and blood type O has no antigens, whereas all other blood groups do.  

The second most common blood group in the UK is A, which accounts for just under 40 per cent of the UK population.

Far less common are groups B (around 10 per cent of the population) and AB (three per cent).

Professor Mypinder S Sekhon, the author of the second study, said: ‘The unique part of our study is our focus on the severity effect of blood type on Covid-19.

‘We observed this lung and kidney damage and in future studies we will want to tease out the effect of blood group and Covid-19 on other vital organs.

‘Of particular importance as we continue to traverse the pandemic, we now have a wide range of survivors who are exiting the acute part of Covid-19, but we need to explore mechanisms by which to risk stratify those with longer-term effects.’

Earlier this year, a study of more than 2,000 coronavirus patients in China found of the 206 who died, 85 had blood type A – equivalent to 41 per cent of all deaths.

It also showed they were more vulnerable to infection and tended to develop more severe symptoms. Those with blood type O had a ‘significantly lower risk’ of getting the disease.

The Chinese team urged medics and governments to consider blood type differences when treating patients with the virus and helping prevent the spread of the disease.

Advice is still to wash your hands and follow the guidelines issued by authorities – whatever your blood type.

And in June, researchers at genetic testing company 23andMe found that people with type O blood were up to 18 percent less likely to test positive for Covid-19.

Additionally, those who had the blood type, and had been exposed, were up to 26 percent less likely to contract coronavirus.

Previous research commissioned by London mayor Sadiq Khan and carried out by Manchester University academics highlighted how black people were nearly twice as likely to die from Covid-19 than white people.

However, experts believe BAME communities have been hit harder by Covid-19 because ethnic minorities are more likely to be poorer and therefore in worse health, and more likely to work in public-facing jobs — leaving them vulnerable to catching the illness.

Public Health England, which found a similar risk of death for BAME people in a long-awaited report published in June, warned historic racism and the hostility towards immigrants was partly to blame.

Dr David Valle, director of the Institute of Genetic Medicine at John Hopkins University, previously said that blood type has been linked in the past to susceptibility to diseases including cholera, and recurrent urinary tract infections from E.coli.

Blood type has been linked in the past to increased susceptibility to diseases. 

A 1977 study found that people with blood type O were actually more likely to become infected with cholera. 

And the authors of a 1993 study suggested that people with type O blood were more likely to become infected with Helicobacter pylori bacteria, which causes stomach bugs and ulcers.    

BAME BRITONS ‘ARE FOUR TIMES MORE LIKELY TO HAVE HAD COVID-19’ 

Black and Asian Britons are up to four times more likely to have had already fought off the coronavirus, official data suggested in the summer.

A government-run surveillance scheme, which tested 36,000 people across England, revealed 4.5 per cent of white people had developed antibodies — substances created by the immune system in response to specific pathogens.

In comparison, the rate was 12.2 per cent for Asian Brits, 7.7 per cent for black people and as high as 16.7 per cent for other ethnic groups, according to the report by the Office for National Statistics (ONS).

Results of swab tests — which tell if someone is currently infected and not if they have had it in the past — showed a similar discrepancy between ethnicity, with between 0.64 and 0.69 per cent of black and Asian people ever testing positive for the coronavirus.

Just 0.30 per cent of white people swabbed between April 26 and June 27 tested positive for the disease.

Results also showed that the risk was nine times higher (2.69 per cent) for people of other ethnic groups, which included Arabs. 

Statisticians warned the findings do not prove for certain that people of BAME backgrounds are at greater risk of being infected.

But they add to the mountain of evidence that has found people of BAME backgrounds are more likely to catch Covid-19 and become seriously ill or die from it than white people.

Add Comment