In COVID-19 naïve KTR with positive cellular response, there was a significant correlation between the percentage of S-protein–specific IFNγ–producing CD8-T cells and total anti-S IgG titers after the third dose (P3: r=0.210, p=0.043) and between the percentage of S-protein–specific IFNγ–producing CD8-T cells and neutralizing titers against the S-protein (P3: r=0.307, p=0.004). This evidence concerns the gene CD8A and COVID-19.