Activated CD4+ T cells reactive against at least one of the spike peptide pools of SARS-CoV-2 were found in 75% of unexposed HC, 81% of post COVID-19 and in 75% and 63% of the HCoVs, respectively (Figures 2A, B, Table 2, and Supplementary Tables 1, 2). Here, CD4 is linked to COVID-19.