A double-blind, randomized, dose-response study of four dilutions of Dryvax in previously vaccinated adults in order to assess the clinical success rates, humoral responses, and virus-specific actifity of cytotoxi T cells and interferon-y producing T cells

Inclusion Criteria:

• For cohort E (never vaccinated): Aged 18-31; Never been vaccinated for smallpox.
• If female, not pregnant or lactating.
• Promise to use an effective method of birth control for 7 months after vaccination.
• Negative result on a test for HIV, AIDS, Hepatitis B and C.
• Acceptable as blood donors.
• For cohorts A, B, C, D (previously vaccinated): Aged 32 to 60 years; known history of smallpox vaccination with a typical vaccinia scar; no smallpox vaccination after 1971.
• Healthy adults (aged 18-60).

Exclusion Criteria:

• Eczema or history of eczema, or other chronic skin disorder.
• Pregnancy or lactation.
• History of immunodeficiency, liver disease, severe kidney impairment, malignancy, HIV, Hepatitis B, or Hepatitis C.
• Household contact with persons who are under 12 months of age, pregnant or lactating, or have any of the specified diseases.