The present invention provides chimeric negative-stand RNA viruses that allow a subject, e.g., an avian, to be immunized against two infectious agents by using a single chimeric virus of the invention. In particular, the present invention provides chimeric influenza viruses engineered to express and incorporate into their virions a fusion protein comprising an ectodomain of a protein of an infectious agent and the transmembrane and cytoplasmic domain of an influenza virus protein. Such chimeric viruses induce an immune response against influenza virus and the infectious agent. The present invention also provides chimeric Newcastle Disease viruses (NDV) engineered to express and incorporate into their virions a fusion protein comprising the ectodomain of a protein of an infectious agent and the transmembrane and cytoplasmic domain of an NDV protein. Such chimeric viruses induce an immune response against NDV and the infectious agent.