Vaccinia Virus Vaccine (APSV) in Vaccinia- Naive Subjects: PILOT

INCLUSION CRITERIA: * Age: 18-32 (Volunteers over 32 years of age are not included since they usually are not vaccinia-naive.) Children are excluded due to concerns of safety, including autoinoculation. * Acceptable medical history by screening evaluation form and brief assessment. * Negative urine pregnancy test for women. * Negative history of smallpox vaccination. * Negative ELISA for HIV or negative Western blot for volunteers who have a positive ELISA and have participated in an HIV vaccine trial. * Availability for follow-up for planned duration of the study (6 months). Note: Stage 1 - clinic visit at Day 180+/-15 days, Stage 2 - phone call at Day 180 +/- 15 days. * If the volunteer is female, she agrees to use acceptable contraception and not become pregnant for the duration of the study. * Willing to sign informed consent. * Adequate renal functions as defined as a serum creatinine of 1.5 mg/dL, urine protein \< 100 mg/dL or negative proteinuria, and a calculated creatinine clearance \> 55 mL/min based on the following formulas: For males ((140 minus age in years) x weight in kg)/72 x serum creatinine). For females: 0.85 x ((140 minus age in years) x weight in kg)/72 x serum creatinine). Note: Renal function is measured to ensure subjects could meet criteria for use of cidofovir if needed. EXCLUSION CRITERIA: * History of immunodeficiency. * Serology positive for HIV, hepatitis B, or hepatitis C at the screening visit. * Known or suspected impairment of immunologic function including, but not limited to, clinically significant liver disease. * Diabetes mellitus. * Moderate to severe kidney impairment. * Malignancy, other than squamous cell or basal cell skin cancer. * Autoimmune disease. * Use of immunosuppressive medication. * Corticosteroid nasal sprays are permissible. * Medical or psychiatric condition or occupational responsibilities that preclude subject compliance with the protocol. * History of "illegal" injection drug use. * Live attenuated vaccines within 60 days of study. * Use of experimental agents within 30 days prior to study. * Any history of vaccination with any vaccinia vectored or other pox vectored experimental vaccine. * Typical vaccinia scar without known history of vaccination. * History of smallpox vaccination. * Acute febrile illness on the day of vaccination. * Pregnant or lactating women. * Eczema or any degree or history of eczema. * History of exfoliative skin disorders/conditions. * Any acute skin disorders of large magnitude, e.g., laceration requiring sutures, burn greater than 2x2 cm. * Receipt of blood products or immunoglobulin in the past 6 months. * Household contacts/sexual contacts with, or occupational exposure to (other than minimal contact), people with any of the following: pregnancy, \< 12 months of age, eczema or history of eczema, previously listed skin disorders/conditions, immunodeficiency disease or use of immunosuppressive medications. * Allergies to any component of the vaccines (e.g. polymyxin B sulfate, dihydrostreptomycin sulfate, chlortetracycline hydrochloride, neomycin sulfate). * Allergies to any known component of the diluent. * Allergies to any known component of VIG, i.e., thimerosal or previous allergic reaction to immunoglobulins. * Allergies to cidofovir or probenicid. * Blood donation within the past 55 days (stage 1 only).