A univariable model revealed that an Hb less than 13 g/dL, WBC greater than 11 × 103/mcL, neutrophils greater than 7 × 103/mcL, lymphocytes less than 1 × 103/mcL and platelets less than 150 × 103/mcL were associated with severe COVID-19. This evidence concerns the gene GSTM1 and COVID-19.