Previous studies have been found that people with O-type blood are at lower risk from coronavirus, while others with blood type A or AB are more susceptible to infection.
However, new research finds no link between blood type and catching the disease or getting seriously ill.
The study included 107,796 people tested for COVID, of which more than 11,000 tested positive.
They compared the blood type of COVID patients with those who tested negative, were hospitalized or non-hospitalized, and those who were in intensive care unit (ICU) with non-ICU patients.
The review found no relationship between ABO blood groups and contracting coronavirus disease.
Also there was no link between blood type and a reduced or increased risk of COVID-19 severity.
The authors wrote:
“The smaller sample sizes and retrospective, observational nature of many prior studies, in addition to their striking heterogeneity of ABO associations with disease susceptibility and severity, could be due to chance variations, publication bias, differences in genetic background, geography and environment, and viral strains.”
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 and will not be useful factors associated with disease susceptibility or severity on either an individual or population level for similar environments and ancestries.”
However, a recent Danish study, which is larger, compared data from nearly half a million people tested for COVID with more than two million non-tested individuals (the control group).
The results suggest that those with blood type O are less vulnerable to the virus and so they have the lowest risk of developing serious illness.
This is because blood group O has no antigens but contains anti-A and anti-B antibodies that are able to neutralize the virus when entering human cells.
Another study analysed the blood group antigens on respiratory and red blood cells and found that SARS-CoV-2 is highly attracted to the blood type A antigen expressed in the respiratory tract.
The study was published in JAMA Network Open (Anderson et al., 2021).