<qa>  How many immunizations will be given at Day 0 and at Weeks 4,Each patient will receive a total of four immunizations to be given at Day 0 and at Weeks 4, 8, and 16. Participants will be randomly assigned to receive either vaccine or placebo. Ten patients will be assigned to each dose group; eight will receive active vaccine and two will receive placebo. The injections will be delivered intramuscularly into the deltoid muscle. In addition to undergoing standard safety exams, patients will have blood drawn for use in evaluating the immunogenicity of the vaccine. The treatment duration will be 16 weeks and patient will be followed for safety and immune responses for an additional 24 weeks after they complete vaccination; the total study is estimated to take 18 months. 