One study suggested that >20 IFN-γ-secreting T cells/106 PBMC as detectable protective influenza-specific T cells at a population level.8 In our repeatedly vaccinated HCW cohort, the prevaccination IFN-γ-secreting T cells increased significantly from non-detectable (5 cells/106 PBMC) to persistently high numbers (95 cells/106 PBMC) after 3−4 vaccinations, although we do not have T-cell data from 2010 and 2011 to confirm whether these cells increased continuously after each year of repeated vaccination until 2012 and 2013, similarly to the antibody responses. This evidence concerns the gene IFNG and influenza.