Viral promoters and compositions and methods of use thereof are provided. Compositions include viruses with impaired ability to reactivate from latency, and pharmaceutical compositions and method of use thereof. The genome of the viruses include one or more mutations that reduce expression from one or more promoters that regulate expression of viral genes during reactivation from latency. The mutation(s) are typically in a region of the viral genome that includes (i) promoter elements of the iP1 promoter of human cytomegalovirus, or the sequence of another virus corresponding thereto (e.g., an iP1 promoter homolog); (ii) promoter elements of the iP2 promoter of human cytomegalovirus, or sequence of another virus corresponding thereto (e.g., an iP2 promoter homolog); or (iii) a combination thereof. In some embodiments the virus encodes one or more heterologous antigens. The viruses can be used as vaccines to induce prophylactic and therapeutic immune responses in subjects in need thereof.