Influenza vaccination is less effective in the elderly compared to the young. Studies that have attempted to identify immune parameters correlating with satisfactory vaccine responses have yielded inconclusive results. Here, we correlate the distribution of different circulating CD4+ and CD8+ T-cell phenotypes with the humoral response to vaccination with Intanza, an intradermal seasonal vaccine, in 54 individuals of different ages. Subjects were stratified according to age (below or over 60) and presence of a latent infection with Cytomegalovirus (CMV). CMV-seropositivity was significantly associated with a lower response rate to the vaccine in people over but not below 60 yr of age. Unlike reported data, late-differentiated (CD45RA+CCR7-CD27-CD28-) CD4+, but not CD8+ T-cells associated with a poorer vaccine response. Thus, latent CMV infection has a deleterious effect on influenza antibody responses in the elderly, which might be mediated through CD4 T-cells lacking CCR7, CD27 and CD28 and re-expressing CD45RA. (C) 2012 Elsevier Ltd. All rights reserved.