The overall aim of this project is to develop an effective vaccine against one of the most common intestinal pathogens, i.e. enterotoxin-producing Escherichia coli (ETEC), especially for use in low and middle income countries. A new oral ETEC candidate vaccine developed by us, consisting of four recombinant strains of E. coli bacteria over-expressing the most important ETEC colonization factors and a toxoid (LCTBA) given alone and together with a mucosal adjuvant, dmLT, is presently evaluated for safety and immunogenicity in adult Swedish volunteers with promising preliminary results. We now plan to evaluate this vaccine in different dosages for safety and immunogenicity in Phase I/II studies in descending age groups; adults, children 2-5 years and young children and infants 6-23 months, in Bangladesh. The project also includes establishment of new methods and determination of optimal time points for assessing mucosal immune responses against the key antigens of the vaccine, in an immunologically primed population. We will also try to identify factors that may explain the lower efficacy of oral vaccines in children in developing countries and based on this identify interventions that may improve immunogenicity in this important target group.. This project was identified by RTI International for their own research purposes and some fields do not align with The GO Map categories. End dates were estimated as one year after the start date. The Project Type "Research, Clinical" may not accurately describe this project's focus but was used for all RTI International's Global Noncommunicable Diseases Initiative projects added in June 2018. Specialties were not analyzed. All project funding was valued in 2015 USD.