The invention is related to polynucleotide-based cytomegalovirus vaccines. In particular, the invention is plasmids operably encoding HCMV antigens, in which the naturally-occurring coding regions for the HCMV antigens have been modified for improved translation in human or other mammalian cells through codon optimization. HCMV antigens which are useful in the invention include, but are not limited to pp65, glycoprotein B (gB), IE1, and fragments, variants or derivatives of either of these antigens. In certain embodiments, sequences have been deleted, e.g., the Arg435-Lys438 putative kinase in pp65 and the membrane anchor and endocellular domains in gB. The invention is further directed to methods to induce an immune response to HCMV in a mammal, for example, a human, comprising delivering a plasmid encoding a codon-optimized HCMV antigen as described above. The invention is also directed to pharmaceutical compositions comprising plasmids encoding a codon-optimized HCMV antigen as described above, and further comprising adjuvants, excipients, or immune modulators.