Certain blood types are believed to make people less susceptible to catching Covid-19, new studies have claimed.
Findings from two independent studies have now indicated that people with blood type O are less likely to pick up the virus than those with blood types A, B and AB.
Risk of complications reduced
Scientists claim that those with blood type O have a lower risk of severe complications, such as organ failure, if they contract the virus - and their risk of death is also reduced.
The four main blood groups are defined by their number of antigen and antibody proteins, with almost half of the UK population (48 per cent) being in blood group O.
People with blood types A and AB are thought to be the most vulnerable, according to the findings, which could explain why some people experience extreme symptoms, while others don’t have any at all.
One research team compared Danish health registry data of more than 473,000 individuals who tested positive for Covid-19 with a control group of over 2.2 million from the general population.
The study found there were fewer positive results among those with blood type O, while there were more among groups A, B, and AB. Infection rates were also similar in these three groups, with trends remaining the same even after scientists accounted for ethnicity, which affects blood group distributions.
A second study of 95 critically ill Covid-19 patients in hospital in Vancouver found similar results, with blood types A and AB blood at higher risk of severe symptoms than those with O or B.
People in the higher risk group were more likely to require mechanical ventilation, suggesting they suffered greater lung damage from the virus, and dialysis for kidney failure. As such, findings indicate that these two blood groups have an increased risk of organ dysfunction or failure due to Covid-19.
People with blood types A and AB also remained in the intensive care unit for a longer period on average, suggesting a greater Covid-19 severity level.
A growing body of evidence
The global biomedical research community is continually working to identify risk factors and potential therapeutic targets as the pandemic continues.
The recent studies, published in the scientific journal Blood Advances, add further evidence to the suggestion that blood types can influence the severity of infection with Covid-19.
Earlier this year, a study of more than 2,000 Covid-19 patients in China found that of the 206 who died, 85 had blood type A, which is the equivalent of 41 per cent of all deaths.
The study also found these people were more vulnerable to infection and typically developed more severe symptoms. By comparison, those with blood type O were again found to have a “significantly lower risk” of getting the disease.
The Chinese researchers have since urged medics and governments to consider blood type differences when treating patients.