The loss in percent CD4+ T cells following COVID-19 for all participants significantly related to older chronological age and increasing epigenetic age inferred from all epigenetic clocks (PCHorvath1, PCHorvath2, PCHannum, PCPhenoAge, and PCGrimAge) (Figure 5), supporting observations of lymphopenia related to COVID-19. This evidence concerns the gene CD4 and COVID-19.