The proportion of infection-elicited IFNγ+, IL4+ and polyfunctional CD4+ T-cells among influenza A/H1N1-infected patients were significantly greater than vaccine-elicited CD4+ T-cells against influenza A/H1N1 (p = 0.033, 0.026 and 0.042 respectively) (Fig. 3 and Supplementary Fig. S4 online). This evidence concerns the gene CD4 and infection.