In contrast, low frequencies of unvaccinated severely ill COVID-19 patients and unvaccinated patients with fatal outcomes significant IFN-γ+CD4+, and IFN-γ+CD8+ T-cell responses specific to α-CCCs/SARS-CoV-2 cross-reactive epitopes (p < 0.001) (Supplementary Table 4). This evidence concerns the gene CD4 and COVID-19.