IFNG and COVID-19: Cross-reactive IFN-γ-producing CD4+ T-cell responses, specific to M176–190, ORF1a1350–1365, S1–13, N388–403, and ORF612–26, and to a slightly lesser extent to ORF8b1–15 and ORF1a1801–1815, were associated with a low COVID-19 severity score (i.e., negatively correlated with an R close to −1) and a very strong negative slope (−41.26 < S < −28.04).