The purpose of this study is to determine whether SF2a-TT15 (a monovalent synthetic carbohydrate-based conjugate Shigella vaccine) is safe and effective in the prevention of Shigella infection. This will be a phase 2b, double-blind, placebo-controlled, single-center study, involving a vaccination phase and a challenge phase. The vaccination phase will consist of study participants that will be 1:1 randomized to receive either the vaccine or placebo. Two doses of blinded study product will be given by intramuscular route of administration, separated by approximately 4 weeks. The challenge phase will consist of an inpatient stay of approximately 12 days during which eligible study participants will ingest an oral inoculum of wild-type S flexneri 2a strain 2457T and then be monitored for illness and treated with antibiotics when the primary endpoint is reached or upon 5 days post-challenge, whichever comes first, or when deemed necessary. Upon satisfying discharge criteria, study participants will complete outpatient clinic follow-up visits through ~7 months after last dose of blinded study product (Day 237). The efficacy study will be enrolled through three cohorts of participants, each cohort consisting of approximately 30 subjects that will be involved in the vaccination phase and 22 subjects that will proceed with the challenge phase. There will be a fourth cohort of participants, consisting of 12 subjects, that will receive the vaccine in an open-label design-this cohort will provide serum samples which are intended to be used for generating serum standards for laboratory assays, as a part of ongoing and future clinical development of Shigella vaccines.
The purpose of this study is to determine whether SF2a-TT15 (a monovalent synthetic carbohydrate-based conjugate Shigella vaccine) is safe and effective in the prevention of Shigella infection.