In COVID-19, there was a decreased ability to produce antiviral cytokines, particularly IFN-γ, and a shift of CD8+ T cells toward a terminally differentiated/senescent phenotype through reducing the number of naive (CD45RA+ CCR7+) and T central memory (Tcm, CD45RA- CCR7+) cells, whereas the frequency of terminally differentiated effector TEMRA (CD45RA+ CCR7-) cells and senescent (CD57+) CD8+ T cells was significantly higher compared to healthy controls. Here, IFNG is linked to COVID-19.