Mutations to the tumor suppressor protein p53 have been observed in 40-60% of all human cancers. These mutations are often associated with high nuclear and cytoplasmic concentrations of p53. Since many tumors exhibit highly elevated p53 levels, the protein is an attractive target for cancer immunotherapy. Unfortunately, p53 is an autoantigen that is likely to be tolerated as a self-protein by the immune system. The present invention is based on the discovery that this self-tolerance can be overcome by administration of recombinant modified vaccinia Ankara (MVA) containing a nucleic acid that encodes p53 (rMVAp53). The invention discloses a method of generating a p53-specific CTL-response to tumor cells expressing mutated p53 by administering a composition comprising rMVAp53. Administration of rMVAp53 decreases tumor development, tumor growth, and mortality in a variety of malignant cell types. These effects are enhanced by administration of CTLA-4 blocker and/or CpG oligodeoxynucleotide immunomodulators.