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