Neoadjuvant chemotherapy is allowed. • Recovery from any toxicity(ies) associated with prior adjuvant therapy. • HER2 expression of 1+ or 2+ by IHC. FISH or Dual-ish testing must be performed on IHC 2+ tumors and shown to be non-amplified by FISH (≤2.0) or by Dual-ish (≤2.0). • HLA-A2, A3, A24, or A26 positive • LVEF >50%, or an LVEF within the normal limits of the institution’s specific testing (MUGA or ECHO) • ECOG 0,1 • Signed informed consent • Adequate birth control (abstinence, hysterectomy, bilateral oophorectomy, bilateral tubal ligation, oral contraception, IUD, or use of condoms or diaphragms) • Must start study treatment (receive first Herceptin infusion) between 3-12 weeks from completion of standard of care therapy. 4.1.3 Exclusion Criteria Patients will be excluded from the study based on the following criteria: CONFIDENTIAL Page 24 of 102 Protocol: HERCEPTIN® + E75/GM-CSF Version 3.1 ML25749 05 March 2017 • Node-negative breast cancer (AJCC N0 or N0(i+)) unless negative for both estrogen (ER) and progesterone (PR) receptors and has received chemotherapy as standard of care • Clinical or radiographic evidence of distant or residual breast cancer • HER2 negative (IHC 0) or HER2 3+ or FISH/Dual-ish amplified (FISH >2.0; Dual-ish >2.0) • HLA-A2, A3, A24 and A26 negative • History of prior Herceptin therapy • NYHA stage 3 or 4 cardiac disease • LVEF <50%, or less than the normal limits of the institution’s specific testing (MUGA or ECHO) • Immune deficiency disease or HIV, HBV, HCV • Receiving immunosuppressive therapy including chemotherapy, chronic steroids, methotrexate, or other known immunosuppressive agents • ECOG ≥2 • Tbili >1.8, creatinine>2, hemoglobin<10, platelets<50,000, WBC<2,000 • Pregnancy (assessed by urine HCG) • Breast feeding • Any active autoimmune disease, requiring treatment with the exception of vitiligo • Active pulmonary disease requiring medication to include multiple inhalers • Involved in other experimental protocols (except with permission of the other study PI) 4.2 METHOD OF TREATMENT ASSIGNMENT If volunteers meet all inclusion criteria and none of the exclusion criteria and agree to participate, they will continue in the study. Patients will be randomly assigned by designated Cancer Insight staff using a computer-generated randomization table to receive Herceptin + E75/GM-CSF or Herceptin + GM-CSF alone. Randomization between the two treatment groups will occur in a 1:1 allocation ratio using an institutional balancing algorithm. Randomization will be stratified by HER2 status (1+ or 2+) and nodal staging (N0 or N1 vs, N2 or N3) (Appendix F). Patients will be blinded as to whether they are receiving Herceptin + E75/GM-CSF or Herceptin + GM-CSF alone. 4.3. STUDY TREATMENT Commercial Herceptin drug will be used and provided free of charge by Genentech. The Sponsor/Investigator of the study will ensure maintenance of complete and accurate records of the receipt, dispensation, and disposal or return of all study drugs in accordance CONFIDENTIAL Page 25 of 102 Protocol: HERCEPTIN® + E75/GM-CSF Version 3.1 ML25749 05 March 2017 with 21 Code of Federal Regulations (C.F.R.), Part 312.57 and 312.62 and Genentech requirements. 4.3.1 Herceptin Formulation Herceptin is a sterile, white to pale yellow, preservative-free lyophilized powder for intravenous (IV) administration. Each vial of Herceptin contains 400 mg of tratuzumab, 9.9 mg of L-histidine HCl, 6.4 mg of L-histadine, 400 mg of α,α-trehalose dihydrate, and 1.8 mg of polysorbate 20, USP. Reconstitution with 20 mL of the supplied Bacteriostatic Water for Injection (BWFI) USP, containing 1.1% benzyl alcohol as a preservative, yields 21 mL of a multidose solution containing 21 mg/mL trastuzumab, at a pH of ~6. 4.3.2 Herceptin Dosage, Preparation, Administration, and Storage a. Dosage The recommended initial loading dose is 8 mg/kg (for q3wk dosing schedules) Herceptin administered as a 90-minute infusion. The recommended maintenance Herceptin dose is 6 mg/kg q3wk and can be administered as a 30-minute infusion if the initial loading dose was well tolerated. Herceptin may be administered in an outpatient setting. DO NOT ADMINISTER AS AN IV PUSH OR BOLUS (see ADMINISTRATION). If different from above the specific dose and regimen of Herceptin to be used should be described here. For this study, a window of +/- 3 days is permitted on the every 3 week dosing schedule. b.