Specific adjuvants that optimize T‐cell activation—such as Alum (aluminum hydroxide), which enhances CD4+ T‐cell activation; MF59 (an oil‐in‐water emulsion used in human influenza vaccines); or CpG oligodeoxynucleotides, which stimulate Toll‐like receptor 9 (TLR9) to boost both T‐ and B‐cell activation [38, 39]—could improve immune responses and promote long‐term immunological memory. This evidence concerns the gene CD4 and influenza.