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.