Experimental Design A. Study design This will be a single institution, single arm phase I -II study designed to examine both the safety and th e immunogenicity of a HER2 CTL peptide -based vaccine when administered concomitantly with trastuzumab to patients with Stage IV breast and ovarian cancer. B. Sample size The number of subjects traditionally required to gather preliminary data on the safe ty of a dose in a phase I study is less than the number needed to evaluate immunologic responses. Since phase I tumor vaccine studies, to date, have proven to be relatively free of serious toxicity, the defining endpoint that would move a study forward to a more extensive phase II efficacy trial will likely be immunogenicity of the vaccine. In order to have meaningful immunologic data we will accrue a target of 20 subjects unless there is excessive toxicity as defined in section 9.0 (see Statistics, Secti on 11). Up to 5 additional subjects can be enrolled to replace patients who withdraw from study for reasons not associated with toxicity. C. Outcome measures Chemical and clinical parameters will be evaluated at baseline, prior to each vaccination and 1 month following the last vaccination to evaluate systemic toxicity (See section 8 for evaluation and management of adverse events and section 10 for stopping rules based on adverse events). Toxicity grading will be evaluated according to NCI common toxici ty criteria (http://ctep.cancer.gov/forms/CTCAEv3.pdf) . All subjects will undergo immunologic response evaluation by cytokine flow cytometry (CFC) on PBMC derived from blood drawn (200 cc) at beginning of study, prior to vaccine # 3, 1 month, 3 months, 6 months and 12 months following the 6 th vaccination or until disease progression (as long immune response is detectable by CFC). Immune response will be defined by CFC. Specifically, a positive immune response will be defined as a post-vaccination antig en specific CD8 or CD4 precursor frequency measured by CFC of < 1:20,000. For subjects who have measurable precursors by CFC at baseline, a positive response will be defined as a 2- fold increase in either antigen -specific T cell subset after vaccination. HLA -A2 MHC tetramer analysis will be used to demonstrate the specificity of the T cells for the HER2 specific HLA -A2 epitopes embedded within the longer immunizing peptides. IFN -gamma secreting PBMC precursor frequency will also be measured by ELIspot in order to determine the development of low level precursor frequencies ( > 1:20,000) not detected by CFC. ELIspot measurements will not be used to define response. All patients will be vaccinated with tetanus toxoid at enrollment to study. This immunization with a foreign antigen (tt) will serve as a measurable vaccinated response for each patient thus confirming immune competence. Overall survival will be followed and compared to historical control. This study will not enroll sufficient numbers of sub jects to give statistical power to this endpoint. However if large difference are observed between the treatment group and historical control, it will give impetus for a sufficiently powered phase II study. 8. Plan of Treatment The following section outl ines the schedule for evaluation and treatment of subjects prior to and during the study. All blood for laboratory evaluations must be drawn before each immunization. 6304p Protocol 118 04/06/2016 A. Prescreen Potential subjects will be screened for eligibility by telephone interv iew with the clinical research staff member to insure that their tumor is HER2 positive as described in eligibility and that they are HLA A -2. Verification that the potential subject meets all eligibility criteria will be made by the P.I . prior to schedul ing the subject for a visit. B.