Safety and Immunogenicity of a Vi-DT Typhoid Conjugate Vaccine

This is a Phase I, Randomized, observer-blinded, age de-escalating study. The study objectives are: 1. To evaluate the safety of 25 μg of Vi-DT typhoid conjugate vaccine administered at 0 and 4 weeks. 2. To assess the immunogenicity of 25 μg of Vi-DT typhoid conjugate vaccine administered at 0 and 4 weeks. 3. To compare the safety and immunogenicity of Vi-DT and Vi-Polysaccharide typhoid vaccines.