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 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.
