A new medical study on the coronavirus in China found that blood type A patients were more susceptible to the infection and tended to develop more severe symptoms, while patients with blood type O seemed more resistant to the disease.

Medical researchers from across China conducted a preliminary study on different blood groups and resistance to the Coronavirus Disease 2019 (COVID-19). Blood group patterns of over 2,000 patients infected with the virus in Wuhan and Shenzhen were studied and compared with that of local, healthy population.

First reported on by the South China Morning Post (SCMP), the study was led by Wang Xinghuan with the Centre for Evidence-Based and Translational Medicine at Zhongnan Hospital of Wuhan University and involved scientists and doctors from Beijing, Wuhan, Shanghai and Shenzhen.

The study found that patients from the O blood group had a “significantly lower risk” for COVID-19 and that those with blood type A may be more vulnerable and might need “particularly strengthened personal protection” against the infection.

From the blood group patterns of more than 2,000 patients studied, the researchers discovered that blood type A patients showed a higher rate of infection and they tended to develop more severe symptoms.

“Sars-CoV-2-infected patients with blood group A might need to receive more vigilant surveillance and aggressive treatment,”  wrote Mr Wang.

The study also found patients with blood type O were more resistant to the disease.

“Blood group O had a significantly lower risk for the infectious disease compared with non-O blood groups,” the researchers wrote in a paper published on Medrxiv.org on March 11.

The blood types of the 206 patients who died from COVID-19 in Wuhan, the epicentre of the virus, were studied. Of the fatalities, 85 had type A blood and 52 had type O. The type A deaths were 63 per cent more than the type O deaths. The study’s authors found that the pattern was present across various age and gender groups.

Blood types are determined by an “antigen”, which is a material on the surface of red blood cells that can trigger an immune response. The main blood groups were discovered by Austrian biologist Karl Landsteiner in 1901—type A, B, AB and O. The medical breakthrough made blood transfusions safer as patients’ blood types could be matched properly.