Additional vaccination study visits will occur at Months 1, 3, and 6. At Months 1 and 3, participants will receive the same vaccine or placebo they received at study entry; at Month 6, participants will receive the VSV HIV gag vaccine or placebo. For 3 days after the study entry and Months 1 and 3 vaccination visits, participants will record their symptoms in a diary. After the Month 6 vaccination visit, participants will record their symptoms for 7 days.