This is a randomized, double-blind, placebo-controlled study. subjects will be randomized to receive investigational vaccine or placebo at a ratio of 3.5:1, MVA3000 to placebo. All subjects will undergo a screening period, a treatment/observation period during which all subjects will receive injections on study day 0 and study day 28 of investigational vaccine or placebo. The clinical observation period will be completed at day 56. A visit will occur at approximately 3 months after the second study injection (study day 118) for additional blood collection and a review of the subject's health status. Follow-up will be obtained via telephone contacts approximately 6 months after the end of the second injection during the treatment/observation period.