Disclosed is a composition comprising an expression system comprising at least one viral vector comprising polynucleotides encoding pneumovirus proteins, and a pharmaceutically acceptable carrier and/or excipient, wherein the expression system comprises a first polynucleotide encoding at least one protein, peptide or variant thereof, which induces a T cell response, and a second polynucleotide encoding at least one protein, peptide or variant thereof, which induces an anti-pathogenic B cell response, wherein the pneumovirus is human respiratory syncytical virus (RSV), and wherein the protein, which induces a T cell response is a non-structural and/or internal protein of a pneumovirus, and/or the protein which induces an anti-pathogenic B cell response is a structural and/or surface protein of a pneumovirus.
