ABO and COVID-19: On the other hand, under co-dominant, recessive, and additive models, the TT (Ser/Ser) genotype of the ABO rs512770 T/C SNP was associated with a high risk of development COVID-19 (OR = 1.87, 95% CI: 1.22–2.88, pCCo-dominant = 2 × 10−3; OR = 1.87, 95% CI: 1.30–2.68, pCRecessive = 5 × 10−4; and OR = 1.35, 95% CI: 1.10–1.67, pCAdditive = 4 × 10−3, respectively) (Table 3).