The purpose of the study is to find out if an investigational drug called Dendritic Cell (DC1) vaccine added to standard neoadjuvant (given before main treatment) therapy can help people with HER2 (human epidermal growth factor receptor 2) positive breast cancer.

Inclusion Criteria:

• Participants must have histologically confirmed clinical stage I- III, HER2+ (per ASCO/CAP criteria) invasive carcinoma of the breast. Primary tumor should measure at least 1 cm by clinical exam or radiologic tests
• Candidate for neoadjuvant chemotherapy with Paclitaxel, Trastuzumab, Pertuzumab regimen followed by standard of care local therapy as determined by the treating physician
• Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1
• Participants must have normal organ and marrow function as defined per protocol.
• Cardiac ejection fraction within institutional normal limits by either Multigated Acquisition Scan (MUGA) or Echocardiogram at baseline.
• Women of child-bearing potential and their male partners must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately. Sexually active male participants should use a barrier method or exercise abstinence during chemotherapy administration until surgery.
• Ability to understand and the willingness to sign a written informed consent document.

Exclusion Criteria:

• Participants with inflammatory breast cancer, widespread locally advanced unresectable disease involving the chest wall/nodal basins in which a curative surgical resection cannot be performed, or those in whom de novo metastatic disease is suspected or confirmed.
• Patients may not be receiving any other investigational agents for the treatment of their breast cancer.
• History of allergic reactions attributed to compounds of similar chemical or biologic composition to the study vaccine components and any of the chemotherapy drugs (paclitaxel, trastuzumab, pertuzumab).
• Participants who are unwilling or unable to undergo an apheresis for production of their vaccine.
• Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.
• Pregnant women and women who are breastfeeding.
• Participants with known congenital or acquired immune deficiency (including those patients who require systemic immunosuppressant drugs for autoimmune disease or organ transplant).