A recent article by Grifoni et al. elegantly demonstrated the ability to measure and understand the human CD4+and CD8+T cell responses to SARS-CoV-2 infection.1These findings highlighted below gave new insights into the immunopathogenesis of COVID-19, the crossreactivity of the SARS-CoV-2 infections, the potential targets of T cells, and for vaccine design. The gene discussed is CD8A; the disease is COVID-19.