In the present study, to find the novel genetic biomarker for the severity of COVID-19, we evaluated a correlation at the population-level between the case fatality rate of COVID-19 and genetic polymorphisms of several potential COVID-19-related genes, including IFITM3, ACE2, TMPRSS2, IL6, LZTFL1, and the ABO genes. Here, ABO is linked to COVID-19.