A large number of studies have shown that CD4+, CD8+ T cell and NK cell were significantly reduced in COVID-19 patients, and were associated with COVID-19 severity and prognosis, and both CD8+ and CD4+ T cell served as diagnostic markers of COVID-19 and predictors of disease severity (Huang et al., 2020; Jiang et al., 2020). This evidence concerns the gene CD8A and COVID-19.