 Approximately 450 healthy adults, 18 to 64 years old, inclusive, will be enrolled into this multicenter, randomized, double-blinded, placebo-controlled, dose-ranging clinical trial. The study will be conducted in 2 stages. During Stage I, 113 subjects who meet the entry criteria for the study will be randomized to receive saline placebo, or 7.5, 15, 45, or 90 mcg of the influenza AH5N1 vaccine by intramuscular injection in an approximate 1:2:2:2:2 ratio N25vaccine dose group and 13 in the placebo group. Subjects will receive 2 doses separated by approximately 28 days. Vaccine administration will be performed by an unblinded vaccine administrator, who will not be involved in subsequent assessments. Subjects will be observed in the clinic for 15 to 30 minutes after inoculation, and subjects will maintain a memory aid to record oral temperature and systemic and local AEs for 7 days after each immunization. Subjects will be contacted by telephone on Day 2 after each immunization to assess for the occurrence of AEs, and they will return on Day 7 for AE and concomitant medication assessment, a targeted physical examination if indicated, and review of the memory aid. Serum for immunogenicity evaluations will be obtained prior to the first vaccination ie, at screening for Stage I and Day 0 for Stage II, prior to the second vaccination, at Day 28, and on Days 56 and 208. All available 7-day safety data following the first dose of vaccine on the 113 subjects enrolled in Stage I will be reviewed by the Safety Monitoring Committee SMC prior to enrollment of the remaining subjects Stage II, who will be followed according to the same protocol. All available 7-day safety data following the second dose of vaccine on the subjects enrolled in Stage I also will be reviewed by the SMC prior to administering the second dose of vaccine to the subjects in Stage II. This study is linked to DMID protocols 07-0022, 05-0006, 05-0090 and 08-0059. 