CD4 and COVID-19: When we summed up all single‐peptide spike‐specific CD4+ T‐cell responses measured for each individual (Figure 1e), the proportion of IFN‐γ+ CD4+ T cells of each subject tended to be higher in the COVID‐19 (median 14.796) and the IV/VI (median 8.117) groups than in the V2/V3 (median 5.385) group.