Ciprofloxacin BioThrax Co-Administration Study

Inclusion Criteria: * Be between 18 and 45 years of age, at the time of enrollment * Be in good health as determined by the investigator from medical history and a physical examination. * If a pre-menopausal female, must be using acceptable methods of birth control. * Be willing and able to return for all follow-up visits and blood and urine collections for the duration of the trial * Be willing and able to complete a web-enabled electronic diary and report concomitant medications, adverse events, and BioThrax reactogenicity events during the trial * Be able to understand and communicate in English. Exclusion Criteria: * Prior immunization with anthrax vaccine or known exposure to anthrax organisms * Intend to enlist in the military during the study. * Have a known allergy to aluminum hydroxide, formaldehyde, benzethonium chloride, or latex. * Plan to receive experimental products 30 days prior to study entry or at any time during the study * Have received a live vaccine in the 30 days before study entry * Plan to receive a live vaccine at any time during the study. * Have ongoing drug abuse/dependence (including alcohol) issues and/or test positive in a urine drug screen for amphetamines, barbiturates, cocaine or opiates * Have received immunosuppressive therapy (including systemic steroids) within 30 days prior to trial entry * Have any other condition known to produce or be associated with immunosuppression * Have received cytotoxic therapy in the previous 5 years * A chronic condition that, in the opinion of the Investigator, would render vaccination unsafe or would interfere with trial evaluations or completion of the study.