The main purpose of this study is to evaluate the safety of each study vaccine and to evaluate the effect on the time to disease recurrence (assessed by disease free survival).

Participants will be assigned to receive one of two study vaccines (DC1 study vaccine vs. WOKVAC). The study vaccine will be administered in two phases: a study vaccination phase and a booster phase.

The total duration of the study will be 6 years (4 years of patient enrollment and 2 additional years of clinical follow-up). Assessment for disease recurrence and survival will be conducted every 6 months (with a phone call/secure email, medical records or follow up visit) from the end of treatment for a total of 2 years, until the completion of the trial or until documented disease recurrence.

Inclusion Criteria:

• Clinical stage I-III HER2 positive breast cancer treated with neoadjuvant chemotherapy including HER-2 directed treatment for at least 12 weeks.

• Residual invasive carcinoma in the breast or axillary nodes in the final pathology from resected tumor following neoadjuvant chemotherapy.

• Completed last cycle of cytotoxic chemotherapy (excluding ado-trastuzumab emtansine [T-DM1]) or radiation > 30 days with resolution of all acute toxic effects of prior therapy to grade ≤ 2 (except alopecia)

• Currently on HER-2 targeted therapy (eg; trastuzumab +/- pertuzumab or T-DM1) per standard of care or has completed HER-2 targeted therapy less than 6 months ago

• Age ≥ 18 years.

• Eastern Cooperative Group (ECOG) performance status 0 or 1.

• Must have normal organ and marrow function as defined below:

  • Absolute neutrophil count (ANC) ≥ 1,000/ μL
  • Platelets ≥ 75,000/ μL
  • Total bilirubin ≤ 1.5 x institutional upper limit of normal (ULN), except patients with Gilbert's syndrome in whom total bilirubin must be <3.0 mg/dL
  • AST/ALT ≤ 3 x institutional upper limit of normal (ULN)
  • Creatinine ≤ 1.5 x institutional upper limit of normal (ULN)
  • Hemoglobin A1C <6.5%

• Left ventricular ejection fraction (LVEF) above institutional lower limit of normal (by echocardiogram or MUGA scan within 90 days of registration).

• Females of child-bearing potential must agree to use dual methods of contraception and have a negative serum pregnancy test at screening, and males must use an effective barrier method of contraception if sexually active with a female of child-bearing potential. For both male and female participants, effective methods of contraception must be used throughout the study and for three months following the last dose.

• Ability to understand and willingness to sign a written informed consent document prior to initiation of any screening or study-specific procedures.

Exclusion Criteria:

• Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, congenital prolonged QT syndrome, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.
• Uncontrolled autoimmune disease requiring active systemic treatment.
• Known hypersensitivity reaction to the Granulocyte-macrophage colony stimulating factor (GM-CSF) adjuvant; any known contraindication to GM-CSF.
• Pregnant or breast feeding.
• Known HIV-positive.
• Known current or a history of hepatitis B or C virus, including chronic and dormant states, unless disease has been treated and confirmed cleared.
• Major surgery within 4 weeks of initiation of study drug.
• Current extended use of immunosuppressive agents or systemic corticosteroids. Topical, ocular, intra-articular, intranasal, inhalational corticosteroids (with minimal systemic absorption) are allowed. A brief course of corticosteroids for prophylaxis (eg., for contrast dye allergy) or for treatment of non-autoimmune conditions (eg., delayed-type hypersensitivity reaction caused by a contact allergen) is permitted.
• Potential participant is currently on active treatment in any other clinical protocol or investigational trial that involves administration of experimental therapy and/or therapeutic devices, or investigational drug.