Similarly, the frequency of exhausted and senescent CD4+ and CD8+ T cells (PD-1+CD57+) increased in the COVID-19 patient from day 14 (7.43 and 56.1%, respectively) throughout the follow-up, peaking on day 24 for CD4+ T cells (25.3%) and day 22 for CD8+ T cells (68.3%) and were dramatically higher than in the HD (1.6% [0.6–6.3] and 18.4%, [14–36], respectively) (Fig. 2c). Here, CD4 is linked to COVID-19.