DISEASE CHARACTERISTICS:

• Histologically confirmed metastatic breast cancer

• Meets 1 of the following criteria:

  • Tumor tissue stains positive with monoclonal antibodies DF3 and/or DF3-P
  • Elevated CA 15-3
• Received at least 1 prior regimen of chemotherapy, immunotherapy, or hormonal therapy
• HLA status known

• Hormone receptor status:

  • Not specified

PATIENT CHARACTERISTICS:

Age

• 18 and over

Sex

• Male or female

Menopausal status

• Not specified

Performance status

• ECOG 0-1

Life expectancy

• Not specified

Hematopoietic

• WBC greater than 2,000/mm^3
• Platelet count greater than 100,000/mm^3

Hepatic

• Bilirubin no greater than 1.5 mg/dL
• SGPT less than 3 times upper limit of normal

Renal

• Creatinine no greater 2.0 mg/dL

Immunologic

• No active or prior extensive eczema or other eczematoid skin disorders
• No active, chronic, or exfoliative skin conditions (e.g., atopic dermatitis, burns, impetigo, varicella zoster, severe acne, or other open wounds or rashes)
• No clinical evidence of altered immune responsiveness
• No immunodeficiency or immunosuppression by disease or therapy
• No autoimmune syndromes (e.g., scleroderma or systemic lupus erythematosus)
• No prior allergic or untoward reaction to vaccinia (smallpox) vaccination
• No allergy to eggs
• No active infection requiring antibiotics
• HIV negative

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for at least 4 weeks after study participation
• No history of seizures, encephalitis, or multiple sclerosis

• Must be able to avoid close household contact with any of the following individuals for at least 3 weeks after study vaccination:

  • Persons with active or prior extensive eczema or other eczematoid skin disorders
  • Persons with acute, chronic, or exfoliative skin disorders
  • Pregnant or nursing women
  • Children under age 5
  • Immunodeficient or immunosuppressed persons (by disease or therapy, including HIV infection)
• No other concurrent serious medical condition that would preclude study participation

PRIOR CONCURRENT THERAPY:

Biologic therapy

• See Disease Characteristics
• Prior vaccinia (smallpox) exposure required
• At least 21 days since prior flu vaccination
• No prior vaccinia vectors or MUC1
• No other concurrent anticancer biologic therapy (e.g., interferon or interleukin)

Chemotherapy

• See Disease Characteristics
• At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas or mitomycin)

Endocrine therapy

• See Disease Characteristics
• At least 4 weeks since prior hormonal therapy
• No concurrent hormonal treatment

• No concurrent steroid therapy

  • Steroid creams or inhalers allowed
• No concurrent dexamethasone or other steroids for antiemetic purposes

Radiotherapy

• At least 4 weeks since prior radiotherapy
• No concurrent radiotherapy

Surgery

• No prior splenectomy

Other

• Recovered from all prior therapy
• At least 3 days since prior antibiotics for active infection