 This study seeks to determine the safety and immunogenicity of a series of 3 primary vaccinations and a booster vaccination of Recombinant ricin toxin A-chain 1-3344-198 rRTA 1-3344-198 vaccine RVEc at 10, 50, or 75 μg IM. This study is evaluating if RVEc will display an acceptable safety profile as determined by adverse event AE data and if RVEc will elicit anti-ricin antibody titers and ricin toxin-neutralizing antibodies in vaccine recipients. 