CD4 and COVID-19: Studying CD4+ and CD8+ T-cell compartments in depth, COVID-19 patients compared with healthy controls showed a significant reduction in the median percentage of naïve CD4+ T cells (CCR7+/CD45RA+): 30.3% (18.8–38.1) vs. 35% (29.3–46.6) (p < 0.001) and CD8+ T cells: 13% (5.5–13) vs. 27.6% (17.8–41.1) (p = 0.028, Table 2).