Gender-based investigations have shown that adult males with COVID-19 fare worse compared to adult females, and a hallmark of this difference in disease course is a relative insufficiency of activated (CD38+, HLA-DR+), as well as terminally differentiated (PD-1+ and TIM-3+) and IFNγ-producing CD8 T cells in adult males with COVID-19 [14]. This evidence concerns the gene HAVCR2 and COVID-19.