The characteristics of patients with moderate and asymptomatic COVID-19 were analyzed, and the results showed that age, cluster of differentiation (CD)8+ (cytotoxic) T cells, C-reactive protein (CRP), white blood cell (WBC) count, neutrophil (NEU) count, lymphocyte (LYM) count, eosinophil (EOS) count, and serum iron were important factors that distinguished patients with asymptomatic COVID-19 from those with moderate COVID-19. This evidence concerns the gene CD8A and COVID-19.