CD4 and COVID-19: Although this relationship is complex to untangle when the peripheral T-cell repertoire is sampled during the acute phase, it is notable that SARS-CoV-2 specific CD4+ T-cells have been associated with lessened COVID-19 severity and that high frequency of Spike-specific CD4+ T-cell responses were observed in patients who had recovered from COVID-19 (10, 29, 38, 39).