CD8A and COVID-19: Although we did not observe any associations between the antibody response to COVID-19 and naïve T cells, there was a significant negative correlation between serum IgG-specific levels for SARS-CoV-2 antigens and senescent CD8+ T cells in the Allele-2 group, which may support the notion that the TT genotype exerts a protective effect through robust CMV-specific T cell responses, as the presence and maintenance of senescent T cells, particularly CD8+ T cells, is a hallmark of chronic CMV infection and also impairs the immune response to vaccination in older adults [20,47].