Results: Significant differences were observed in the genotypic distribution of PPARG rs17793951 between the two groups (p = 0.001), and the PPARG rs17793951 AG + GG genotype was associated with a higher risk of low responsiveness to influenza vaccine adjusted for gender and age (additive genetic model: OR = 2.94, 95% CI = 1.67–5.19, dominant genetic model: OR = 2.81, 95% CI = 1.61–4.92). This evidence concerns the gene PPARG and influenza.