CD8A and viral infectious disease: Recent studies, adopting the live attenuated yellow fever virus (YFV) vaccine as a model to study acute viral infection in humans, have indicated that CD8 T cells against HLA-A2- and HLA-B7-restricted epitopes display a CD45RA−CCR7− phenotype during the peak effector response, which transits into a CD45RA+CCR7− phenotype at the memory stage [20, 21].