The present invention provides a population of live attenuated recombinant replication-competent viruses, which population comprises at least two member viruses, each of the member viruses comprising a nucleotide sequence encoding a different antigenic polypeptide from a source other than a parent virus from which the recombinant virus was derived. When a eukaryotic cell of a mammalian host is infected with a member of the population, the nucleotide sequence is expressed, the antigenic polypeptide is produced, and elicits an immune response. The invention further provides compositions, including immunogenic compositions, comprising a subject virus population. The invention further provides methods of eliciting an immune response to a polypeptide in an individual, involving administering a subject virus population. The invention further provides devices for use in eliciting an immune response.