Regarding poly I:C, it was reported that the administration of poly I:C as an adjuvant in an H9N2 influenza vaccine significantly induced higher antibody titers and elevated expression levels of IFN-α, IFN-γ, IL-6, and major histocompatibility complex class II (MHC-II) in ducks [54]. This evidence concerns the gene IFNA1 and influenza.