Studies from our group and others have detected cross-reactive CD4+ and CD8+ T cells, directed toward specific sets of conserved SARS-CoV-2 epitopes, not only from unvaccinated COVID-19 patients but also from a significant proportion of unexposed pre-pandemic healthy individuals (UPPHI) who were never exposed to SARS-CoV-2 (33, 50, 76, 77). Here, CD4 is linked to COVID-19.