These changes have led to the identification of immune biomarkers; senescent T-cells were predictive of influenza vaccine failure in two community dwelling elderly cohorts [5,6] and an immune risk profile characterized by a CD4+/CD8+ ratio less than 1 (due to the expansion of the CD8+ T-cell pool relative to CD4+ T-cell pool) was predictive of both mortality and chronic infection with cytomegalovirus (CMV) in aging Swedish cohorts [4,7-9]. This evidence concerns the gene CD4 and influenza.