CD4 and COVID-19: Strikingly, reductions in entropy and increases in dominance were now even more overt for those aged ≥50 y, being significant for CD4+ and CD8+ cells by all measures (SI Appendix, Fig. S8 A and B), whereas no significant changes were observed for patients with COVID-19 aged <50 y (SI Appendix, Fig. S8 A and B).