GSK-4001785A

The aim of the current clinical study is to evaluate, for the first time in humans (FTIH), the safety and immunogenicity of the altSonflex1-2-3 candidate vaccine against S. sonnei and S. flexneri serotypes 1b, 2a, and 3a. The vaccine will be first administered in adults 18 to 50 years of age in Europe. Subsequently, the vaccine will be administered to a shigellosis-endemic population in Africa, first in adults 18 to 50 years of age, then in children 24 to 59 months of age, and finally in infants 9 months of age. Infants will also receive a third vaccination. Three different doses of the vaccine [low (Dose A), medium (Dose B), and high (Dose C) amounts of antigen] will be evaluated using an age de-escalation approach (from least vulnerable adult population to most vulnerable paediatric population). The results of this study will allow the selection of the most appropriate dose for further vaccine development in infants 9 months of age, which is the main target age group for this vaccine.