Inclusion Criteria:

   - Signed Informed Consent

   - Women, ≥ 18 years of age

   - Histologically documented, HER-2 (+) breast cancer with metastatic disease.

   - Evaluable or measurable disease. PATIENTS MAY BE NED. Patients must be assessed as
   having stable disease or better at the end of 1st- or 2nd-line chemotherapy. In
   addition, patients must have a tumor assessment within 28 days of the first planned
   dose of MVA-BN®-HER2, and have a response status of SD or better.

   - Prior chemotherapy for metastatic breast cancer

   - Completed 1st- or 2nd-line chemo for mBrCA at least 3 weeks (from the date of the last
   dose) prior to the first dose of MVA-BN®-HER2

   - ECOG Performance Score of 0, 1, or 2

   - Life expectancy ≥ 6 months

   - Left ventricular ejection fraction (LVEF) by ECHO or MUGA ≥ LLN

   - Women of childbearing potential must have a negative serum or urine pregnancy test,
   and must agree to use a medically acceptable barrier and/or chemical method of
   contraception throughout the study treatment period and for 28 days after the last
   dose of MVA-BN®-HER2

   - No significant cardiac, bone marrow dysfunction, or coagulopathy. No significant
   hepatic or renal dysfunction.

   - A negative virology screen for HIV, hepatitis B surface antigen, hepatitis C, and
   HTLV-1

Exclusion Criteria:

Patients may not have:

   - Known history of metastasis to the central nervous system

   - Congestive heart failure (NYHA Class III or IV), unstable angina, or cardiovascular
   disease such as stroke or myocardial infarction (current or within the past 6 months)

   - History of prior malignancies other than breast cancer within the past 5 years,
   excluding basal or squamous cell carcinoma of the skin or carcinoma in situ of the
   cervix

   - Known allergy to eggs, egg products, or aminoglycoside antibiotics, e.g., gentamicin
   or tobramycin

   - Chronic administration (5 or more consecutive days) of systemic corticosteroids within
   14 days of the first planned dose of MVA-BN®-HER2.

   - History of or active autoimmune disease. Persons with vitiligo or thyroid disease
   taking thyroid replacement hormones are not excluded.

   - Prior solid organ or hematopoietic allogenic transplant(s)

   - Prior use of hematopoietic growth factors (e.g., GM-CSF) within 28 days of the first
   planned dose of MVA-BN®-HER2

   - Receipt of an investigational agent within 28 days of the first planned dose of
   MVA-BN®-HER2

   - Prior "vaccine" therapy for breast cancer at any time

   - Vaccination: Vaccinations with a live (attenuated) vaccine within 28 days of the first
   or last dose of study drug; or vaccinations with a killed (inactivated) vaccine within
   14 days of the first or last dose of study drug.

   - A maximum cumulative dose of prior doxorubicin > 360 mg/m2 or epirubicin > 720 mg/m2

   - Radiation therapy within 28 days of the first planned dose of MVA-BN®-HER2 or plans
   for radiation therapy after enrollment.

   - Pregnant, lactating, or nursing

   - Any condition which, in the opinion of the investigator, would prevent full
   participation in this trial or the long-term follow-up study, or would interfere with
   the evaluation of the trial endpoints