The percentage of CD4+Th cells was significantly lower, while CD8+ Tc cells were significantly higher in the total Omicron COVID-19 patients group and the vaccinated Omicron COVID-19 patients group compared to the total mild SARS-CoV-2 patients (2020) group and uninfected control (Table 2, Figure 2) (p < 0.05 in each). The gene discussed is CD8A; the disease is COVID-19.