The analysis showed significantly lower levels of IFN-γ production in response to A/H1N1/Brisbane/59/2007, A/H1N1/Solomon Islands/3/2006 and B/Florida/4/2006 in blood from study participants who had previously received seasonal flu vaccination (during the period 2006 to spring 2009) and who did not receive the pdm flu vaccine, than in those without any seasonal flu (or pdm) vaccination during the same period (p ≤ 0.04). This evidence concerns the gene IFNG and influenza.