COVID-19 patients also showed a decreased median proportion of early-activated Th1 (ICOS+/PD-1-): 0.3% (0.2–0.6) vs. 1.7% (0.7–2.1) (p < 0.001), Th2: 0.4% (0.2–0.8) vs. 2.81% (1.3–3.6) (p < 0.001) and Th17: 0.2% (0.1–0.4) vs. 1.2% (0.6–1.8) (p < 0.001). Here, ICOS is linked to COVID-19.