CD4 and COVID-19: It was shown that accelerated pathogen recognition and the early appearance of SARS-CoV-2-specific CD4+ T cells in circulation had the strongest association with the severity of COVID-19, since effective and early induction of these T cells in acute COVID-19 has resulted in a milder form of the disease with accelerated viral clearance, whereas the lack of SARS-CoV-2-specific Th cells was closely linked with severe COVID-19 (reviewed in [6]).