A cancer vaccine consisting of a truncated recombinant HER2/neu peptide (dHER2) combined with the immunoadjuvant AS15 with potential immunostimulatory and antineoplastic activities. Upon administration, dHER2+AS15 vaccine may stimulate the host immune response to mount a cytotoxic T-lymphocyte (CTL) response against tumor cells that overexpress the HER2/neu protein, resulting in tumor cell lysis. The tumor-associated antigen (TAA) HER2/neu is often overexpressed by a variety of tumor cell types; dHER2 includes amino acids 1-645 or 1-653 of the extracellular domain (ECD) and an immunogenic carboxyl terminal autophosphorylation portion of the intracellular domain (ICD). AS15 is an adjuvant formulation that contains the adjuvant systems AS01B and AS07A; AS01 B is composed of liposomes containing 3D-MPL and QS21 and AS07A is composed of the synthetic oligodeoxynucleotide (ODN) Toll-like receptor-9 (TLR9) agonist CpG 7909.