We have shown that in older adults, vaccination with current inactivated influenza vaccines provides only a weak stimulus to the production of IFNγ by both CD4+ and CD8+ T cells Kumar et al. (2017) and to the production of the cytolytic mediator, granzyme B (GrB), as well as the generation of cytolytic CD8+ T cells in response to ex vivo influenza A/H3N2 challenge (McElhaney et al., 2006; McElhaney et al., 2009; Shahid et al., 2010; Zhou and McElhaney, 2011; Haq et al., 2017; Kumar et al., 2017). Here, CD4 is linked to influenza.