If records are not available, patients, or their referring physicians, will be contacted to discern their disease status. All enrolled patients, regardless of randomization will be followed for clinical recurrence for three years from the date of initiation of trastuzumab maintenance therapy. The primary outcome measure of the trial is invasive DFS. 3.3.2 Secondary outcome measures Secondary outcome measures include determining DRFS from initiation of trastuzumab maintenance therapy, assessing local and systemic toxicities, and evaluating immune responses. Distant recurrence free survival will be assessed as part of the patient’s disease state determined by their physician at the individual study sites during routine follow-up screening (see 3.3.1 Primary outcome measure). Determination of DRFS will allow for continued follow-up on patients with local or regional recurrence. Standard local and systemic toxicities will be collected and graded per the NCI Common Terminology Criteria for Adverse Events (CTCAE) version 4.03 graded toxicity scale (Appendix C). For both the inoculations during the PVS and the booster inoculations, the patient will be monitored for 30 minutes with vital signs taken as needed. Patients will either return to their study site or be contacted by 17 Protocol: 2014-0443 Version 2.1 Version Date: 11 April 2016 phone for questioning regarding any systemic and local toxicity during the initial 48-72 hours after inoculation. If they return to their study site, the local reaction at the inoculation sites will be examined and measured. For patients that do not return to the study site, a tool will be given and instructions provided to measure the local reaction. Serious AEs will be reported as described in Section 5. Immune responses will be primarily documented using the delayed type hypersensitivity (DTH) reaction and using the dextramer assay to enumerate peptide-specific CTL. Each of these measurements will be performed regardless of randomization. Detailed descriptions of these assays/tests are described in Sections 4.4.6 and 4.4.8. DTH reactions will be measured prior to initiation of the vaccination series, one month ± 1 week after completion of the PVS, and one month ± 1 week after the final booster inoculation. Dextramer measurements will be performed prior to initiating the vaccination series as well as one month ± 1 week after completion of the PVS. Additionally, these assays may be performed pre- and post-each booster.