CD8A and COVID-19: SARS-CoV-2-specific CD4+ and CD8+ T cells are found in peripheral blood from COVID-19 patients in the first two weeks after symptom onset, and the majority of these CD4+ T cells exhibit a central memory phenotype with a dominant production of Th1 cytokines, while CD8+ T cells have a more effector phenotype with high levels of perforin expression [459].