Yersinia (Y.) pestis, a gram-negative coccobacillus, causes an acute and often fatal disease that may appear in 1 of several major manifestations: bubonic, septicemic, and pneumonic. Transmission to humans most commonly occurs via a bite by infectious fleas and is associated with regional lymphadenopathy or bubo. Pneumonic plague would be the most likely outcome in the case of a bio-terrorism attack. Currently, there is no effective licensed vaccine that protects against pneumonic plague. The investigational product, flagellin/F1/V in phosphate-buffered saline, pH 6.2, is a vaccine that is designed to provide protection against respiratory exposure to Y. pestis, i.e., pneumonic plague. The general hypothesis to be tested is that the flagellin/F1/V vaccine will induce a robust humoral immune response against the F1 and V antigens of Y. pestis without serious adverse events (SAEs) when the vaccine is given intramuscularly (IM) on 2 occasions separated by about 28 days at doses of 1, 3, 6 and 10 micrograms (mcg). Since the major rationale for this vaccine is protection against respiratory exposure to Y. pestis following a bio-terrorism attack, the initial study population will be 18-45 year old healthy volunteers. The primary objective of this study is to assess the safety and immunogenicity of escalating dosages of Flagellin/F1/V vaccine among healthy subjects given 2 doses of vaccine by the IM route on Days 0 and 28. The secondary objective of this study is to evaluate the reactogenicity and cell mediated immune responses of escalating dosages of Flagellin/F1/V vaccine among healthy subjects when given 2 doses of vaccine by the IM route on Days 0 and 28. Participants will include up to 48 healthy male and female volunteers. This study is designed as a randomized, placebo controlled, double-blind (within dosing group), dose escalation Phase I study. The study will consist of 4 groups to be dosed sequentially. Each group will consist of 10 individuals that receive vaccine and 2 that receive placebo. Each subject will receive an IM vaccination on Days 0 and 28. The initial dose to be evaluated will be 1 mcg/dose. Following assessment of safety and reactogenicity data of each group by the Safety Monitoring Committee the vaccine doses will be increased sequentially from 1, to 3, to 6, to 10 mcg/dose. Following vaccination, subjects will return to the clinical site on Days 1, 14, and 28 following the initial vaccination and on Days 1, 14, 28, 40, and 180 following the second vaccination. In addition, subjects will be contacted by phone on Day 3 after each vaccination to review the memory aid, query for adverse event (AEs)/SAEs and concomitant medications. All subjects will complete a subject memory aid for 15 days following each vaccination (Day 0-14). Unsolicited, non-serious AEs will be collected through Day 56 (Visit 8, 26-30 days following the final vaccination). SAEs will be collected throughout the study period Day 393 (Visit 11, 365 days + 14 days after the second vaccination). Blood samples for safety labs will be collected at screening, day of initial vaccination and at 14 days after each vaccination. Specimens will be collected for immunologic assays at the noted clinic visits, as well as at 6 months post the final vaccination.