Across the entire vaccination cohort, the proportions of NK cells producing IFN-γ and degranulating (i.e., expressing CD107a at the cell surface) in response to high concentrations of IL-12 plus IL-18 were significantly higher after vaccination, with increased frequencies compared with baseline values both 2 wk (29 out of 52 individuals) and 4 wk (32 out of 52 individuals) after influenza vaccination. Here, IL18 is linked to influenza.