More on 'Association between ABO blood groups and risk of SARS-CoV-2 pneumonia'.

: We read with interest the recent report from Li and colleagues describing an association between ABO blood groups and risk of SARS-CoV-2 pneumonia [1]. In an initial study of 265 patients with COVID, the authors observed that blood group O individuals were significantly under-represented amongst patients who required hospitalization for severe COVID-19 infection (p < 0.01). Conversely, blood group A was significantly more common in patients with severe COVID-19 compared to the local population (p=0.017). Subsequently, in a larger validation cohort that included 2153 patients with COVID-19, this ABO effect was reproduced with blood group O again being associated with a significant protective effect (p < 0.001). In keeping with these data, another independent study (n=2173) also reported that blood group O was associated with reduced susceptibility to severe COVID-19.