Volunteers receive one of two schedules of vaccines or placebo administered at days 0, 28, and 168. Specifically, group 1 receives oral microparticulate monovalent vaccine over 3 consecutive days on days 0, 1, and 2, and 28, 29, and 30, with the intramuscular monovalent vaccine given on day 168. Group 2 receives the intramuscular vaccine first, on day 0, followed by the oral form given on days 28, 29, and 30 and 168, 169, and 170. Volunteers are followed for 1 year.

Inclusion Criteria

Volunteers must have:

• Normal history and physical exam.
• HIV negativity.
• CD4 count >= 400 cells/mm3.
• Intermediate or high risk sexual behavior or a history of injection drug use within 12 months prior to study entry.
• Normal urine dipstick with esterase and nitrite.

Exclusion Criteria

Co-existing Condition:

Volunteers with the following symptoms or conditions are excluded:

• Active tuberculosis.
• Occupational or other responsibilities that would prevent completion of study.

Volunteers with the following prior conditions are excluded:

• History of immunodeficiency, chronic illness, autoimmune disease, or use of immunosuppressive medications.
• Psychiatric, medical, or substance abuse problems within the past 6 months that would affect ability to participate in study.
• History of anaphylaxis or other serious adverse reactions to vaccines.
• History of inflammatory gastrointestinal disease, celiac disease, or intestinal malignancy.
• Acute gastroenteritis or gastrointestinal surgery within the past 12 months.

Prior Medication:

Excluded:

• Live or attenuated vaccine within the past 60 days.
• Illicit or experimental agents within the past 30 days. Intermediate or high risk sexual behavior. Injection drug use within the past 12 months.