The present invention provides safe, stable, efficacious, and cost-effective vaccines based on viral expression vectors that include a parainfluenza virus 5 (PIV5) genome including a heterologous nucleotide sequence expressing a heterologous polypeptide. In some embodiments, the heterologous nucleotide sequence is inserted closer to the leader than between the hemagglutinin-neuroaminidase (HN) gene and the large RNA polymerase protein (L) gene of the PIV5 genome. In some embodiments, the heterologous nucleotide sequence is inserted between the small hydrophobic protein (SH) gene and the hemagglutinin- neuroaminidase (HN) gene of the PIV 5 genome.
