Among this age group, despite lower antibody responses of qIRV compared with the licensed QIV control for the B strains (as measured by HAI GMTs, GMFRs, and seroconversion), higher IFNγ-producing CD4+ and CD8+ T-cell responses to all four influenza strains were elicited following qIRV compared to licensed QIV. This evidence concerns the gene CD4 and influenza.