The present invention provides a recombinant viral vector, an immunogenic composition containing the same, and the use thereof. The recombinant viral vector comprises a polynucleotide encoding a fusion peptide of CD4 helper T cell epitopes, the epitope fusion peptide comprising a cytomegalovirus epitope and/or an influenza virus epitope. The epitope fusion peptide and the recombinant viral vector provided by the present invention can improve the level of cellular immune response to a target immunogen, particularly to a weak immunogen, and overcome the immune tolerance of immune system to an antigen, particularly to a tumor antigen or an infection-related antigen. The products of the present invention are suitable for enhancing the efficacy of vaccines.