T helper (Th) cells expressing IL21 (1–10%), TGFB1 (2.9–9.5%), and IL21 plus TGFB1 (0.3–3.5%) were as frequent among the SARS-CoV-2-reactive Th cells as among measles-reactive Th cells of a healthy control (2%, 6%, 0.6%, Fig. 5). The gene discussed is IL21; the disease is measles.