Disclosed herein are methods of treating or preventing prostate cancer in a subject, the methods comprising administering to the subject a treatment regimen comprising two or more vaccines comprising a great ape adenovirus serotype 20 (GAd20) virus that, in turn, comprises a nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 1 and one or more vaccines comprising a Modified Vaccinia Ankara (MVA) virus that, in turn, comprises a nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 3 to thereby treat or prevent the prostate cancer.