Dose Ranging Study to Determine the Safety, Reactogenicity and Immunogenicity of Typhoid Fever Vaccine (Ty800) in Healthy Adult Subjects

Inclusion Criteria: * Healthy Males or Females aged 18 to 55 years, inclusive * Capable of understanding and complying with the protocol requirements and be available for the duration of the protocol Exclusion Criteria: * History of malignancy, immunocompromised conditions or currently receiving immunosuppressive treatment including systemic steroids * History of Typhoid Fever infection, vaccination against typhoid fever or participation in a Clinical Trial using S.typhi organism at any time * History of travel to a typhoid endemic region within the last 5 years or history of raising a child from an endemic area. Endemic regions are South and East Asia, the Indian Subcontinent, Africa and Central and South America including Mexico * History of persistent diarrhea, blood in stool, peptic ulcer disease, or inflammatory bowel disease * Allergies or sensitivities to antibiotics, notably quinolones, penicillins, sulfonamides, cefalosporins and chloramphenicol, and components of the buffer solution, notably aspartame. * People who are commercial food handlers, day care workers, or health care workers involved in direct patient care. Also people with young children under 2 years of age at home or household contacts who are immunocompromised, pregnant or breast-feeding