CD4 and COVID-19: SARS-CoV-2-specific CD4+ T cells showed a greater correlation with reduced severity of COVID-19 than antibodies and CD8+ T cells, while successful generation of SARS-CoV-2-specific CD4+ T cells at the early onset of the COVID-19 was correlated with increased viral clearance and, thus, moderate the disease (Rydyznski Moderbacher C et al., 2020; Sette and Crotty, 2021).