The kinetics of contraction of CD8 and CD4 T cells appears to slightly differ; both SARS-CoV-2-specific CD4 and CD8 T cells are present within the first 2 weeks after onset of symptoms, but while CD8 T cells show signs of progressive reduction after viral clearance (>1 month after infection) [20, 30], the SARS-CoV-2 CD4 T-cell frequency is more stable and appears higher in individuals tested in the initial recovery phase (1–2 months after infection) than immediately after infection [20]. This evidence concerns the gene CD4 and infection.