PATIENT SELECTION A. Inclusion criteria 1. Patients must have received at least 1 vaccination of the HER2 CTL peptide -based vaccine. 2. Patients must have Stage IV breast cancer with either no evidence of disease, disease that is stable, or slowly progressive disease. 3. Patients taking HER2 -targeted monoclonal antibody therapy may remain on the treatment. a. HER2 -targeted monoclonal antibody therapy is defined as either trastuzumab monotherapy, or trastuzumab and pertuz umab combination therapy administered per standard of care. 4. Patients must be at least 28 days post cytotoxic chemotherapy prior to first vaccine 5. Patients on bisphosphonates and/or endocrine therapy are eligible and may remain on therapy. 6. Patients must be at least 28 days post immunosuppressants prior to first vaccine. 7. Patients must have an ECOG Performance Status Score ≤ 1 (Appendix A of original protocol). 8. Non-menopausal female subjects who are having sex that can lead to pregnancy must agree to contraception for the remainder of their childbearing years. 9.