Safety Study of MVA Smallpox Vaccine in HIV-positive Subjects Who Are Vaccinia Naive

Inclusion Criteria: * Adults at least 18 years old and who were born after 1971 who have never had a smallpox vaccination or exposure to a vaccinia-containing product * Subjects must test positive for HIV infection * Subjects must be in good general health except for HIV infection, including no AIDS-defining illnesses. * Female Subjects must not be pregnant or lactating, and all subjects must agree to practice birth control * subjects must be clinically stable for 6 months prior to study enrollment. Exclusion Criteria: * Subjects with a known or suspected history of immunodeficiency (with the exception of HIV infection) * Subjects with history or prior exposure to a vaccinia-containing product * subjects with current radiation treatment or use of immunosuppressive or antineoplastic drugs (with exceptions) * Subjects with concomitant illnesses associated with impairment of immunologic function. * subjects with dementia * Subjects with malignancy. * Subjects with a known history of Cardiac disease, or who have risk factors for ischemic coronary disease, or other abnormalities * Current or past history of eczema * known allergies to any component of MVA, including eggs or egg products, or allergies to blood products * females must not be pregnant and using approved contraceptives. * Morbid obesity