Influenza A viruses have the potential to cause worldwide epidemics and/or pandemics resulting in significant morbidity and mortality. Two-hundred twenty-six healthy male and female subjects aged 18 to 49 years, inclusive, in the United States (US) will be enrolled into this single-center, randomized, double-blinded, placebo-controlled trial of intradermal (ID) and intramuscular (IM) injection with subvirion (SV) inactivated influenza A/H5N1 vaccine. The study will have two vaccine groups. Vaccine group 1: the subject will receive 0.1 mL of H5 Hemagglutination (HA) by the ID route in one arm and 0.1 mL of saline placebo by the IM route in the other arm. Vaccine group 2: the subject will receive 0.1 mL of H5 HA by the IM route in one arm and 0.1 mL of saline placebo by the ID route in the other arm. All eligible subjects will be enrolled and randomized 1:1 (113 subjects per vaccine group) to either vaccine group 1 or vaccine group 2. All subjects will receive two doses of approximately 30micrograms of H5 HA by their assigned route, either IM or ID, separated by approximately 28 days. At each vaccination visit, all subjects will also receive a saline placebo in the opposite arm by the different route as their vaccine route (i.e. if vaccine is administered by the ID route in one arm, then a saline placebo will be administered by the IM route in the opposite arm). The second vaccine dose will be administered by the same route as per vaccine group assigned at original randomization. Subjects will be observed in the clinic for approximately 15 minutes after each vaccination. Subjects will return on Day 2 for arm check and assessment of adverse events. All subjects will maintain a memory aid recording oral temperature, and systemic and local adverse events for 7 days after each vaccination. They will return to clinic on Day 8 for adverse event (AE) assessment, concomitant medication assessment, a targeted physical exam (if indicated), and review of memory aid. AE data will be captured Day 0 through Day 56. Serious AE data will be captured from Day 0 through the end of each subject's participation in the study (approximately 7 months). The subjects, staff assessing subjects, and lab personnel will be blinded. Serum for immunogenicity evaluations will be obtained prior to the first vaccination, at Day 0; prior to the second vaccination, at Day 28; on Day 56 and approximately Day 208 (7months after dose 1). The primary objectives are to compare the immunogenicity of a similar dosage level of a subvirion inactivated influenza A/H5N1 vaccine given by ID or IM injection one month after receipt of the second dose of vaccine and to compare the safety and reactogenicity of ID and IM immunization at a similar dosage level of a subvirion inactivated influenza A/H5N1 vaccine among healthy young adults. The secondary objective is to evaluate serum antibody responses approximately 1 and 7 months after the first vaccination. This study is linked to Division of Microbiology and Infectious Diseases protocol 07-0022.