ABO and COVID-19: COVID-19 severity-related genes (SLC6A20, LZTFL1, FOXP4, TMEM65, ABO, OAS1, TAC4, DPP9, TYK2, ZBTB11, IL10RB, KANSL1, PLEKHA4, and IFNAR2) and single nucleotide polymorphisms (SNPs) identified by genome wide association studies were summarized in Table S1 (5–9).