the application discloses therapeutic vaccines based upon the “ ping ” dna plasmid vector expressing the gene encoding the rat her2 protein . vaccines according to the instant disclosure are used as an adjunct treatment for surgery , radiation and / or chemotherapy for dogs and cats with cancers that over express the her2 antigen , and prolong the post - surgical disease free interval and / or survival time . also included are therapeutically effective methods of immunization using said vaccines .