Clonal expansion of CD8 + T cells was observed in the lung tissues of patients with COVID-19,9 and in the peripheral blood of convalescent individuals.10 Expansion of CD8 + T cells was demonstrated to be related with milder disease severity and better viral clearance.11 Thus, CD8 + T cells which are specific to virus can be the main force for virus clearance, but its attack ability may be impaired by the continuous mutation of SARS-CoV-2, just like the neutralizing antibody. The gene discussed is CD8A; the disease is COVID-19.