Age-descending Phase 2 trial to assess safety and immunogenicity of a Trivalent Salmonella (S. Enteritidis, S. Typhimurium, S. Typhi Vi) Conjugate Vaccine for sub-Saharan Africa

Should the TSCV Phase 2 study achieve the anticipated positive results, this would pave the way for subsequent studies in the clinical development plan. These include a TSCV/EPI vaccine non-interference study, to demonstrate that TSCV can be co-administered with routine EPI vaccines given at the visits when TSCV will be offered, without increasing reactogenicity or diminishing immune responses compared to when TSCV and the EPI vaccines are administered at least two weeks apart. The complexity and cost of this large Phase 2 non-interference study is driven by the need to use validated serological assays to document non-inferiority. Some EPI vaccines such as pentavalent (DPT/Hib/HBV) and 13-valent pneumococcal conjugate vaccines incorporate many vaccine antigens to which validated antibody responses must be measured. This key future Phase 2 study would clear the path for a Phase 3 randomized, controlled field trial to assess TSCV’s efficacy in preventing iNTS disease. Licensure of TSCV as a typhoid vaccine can be achieved by documenting non-inferiority of anti-Vi responses when TSCV vaccine is administered versus anti-Vi titers elicited by Typbar-TCV. TSCV, like MenAfriVac, is a conjugate vaccine developed specifically to address a sub-Saharan African need. One key to MenAfrivac’s success was a low cost of goods.