Provided are methods to induce and maintain a protective cytotoxic T-lymphocyte response to a peptide of the HER/neu oncogene, GP2, with the effect of inducing and maintaining protective or therapeutic immunity against breast cancer in a patient in clinical remission, including patients having low to intermediate levels of HER2/neu expression. The methods comprise administering to the patient an effective amount of a vaccine composition comprising a pharmaceutically acceptable carrier, an adjuvant such as GM-CSF, and the GP2 peptide. The methods may further comprise administering a periodic booster vaccine dose as needed due to declining GP2-specific T cell immunity. Also provided are vaccine compositions for use in the methods.
