Will your blood type save you?
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.
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.
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 Covid19 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.