Lower SARS-CoV-2-specific CD4+ T cell counts correspond with higher disease severity. (a). Kinetics of circulating CD4+ and CD8+ T-cells specific to SARS-CoV-2 spike, nucleocapsid, and membrane peptides, in relation to the day of viral clearance. (b). Maximum values grouped by the time to viral clearance: ≤ 21 (blue)/> 21 (red) days. Lines indicate non-linear group trends. Spline regression with bootstrap confidence intervals. (c). Maximum values and average daily severity scores per patient, grouped by the time to viral clearance: ≤ 21 (blue)/> 21 (red) days. (d). Maximum values grouped by non-ICU (blue)/ICU (red) patients. SARS-CoV-2 CD4+ (%) = percentage of CD154+CD137+ out of total CD4+ T cells, SARS-CoV-2 CD8+ (%) = percentage of CD137+IFNg+ out of total CD8+ T cells. S.CoV-2; SARS-CoV-2. n = 34 patients, 130 samples. Mann–Whitney U test.