The highest incidence, morbidity, and mortality of shigellosis is in young children. But serum antibody responsiveness to it is age dependent and infants and young children respond poorly or not at all to polysaccharide antigens following disease, administration of attenuated strains of Shigella or vaccination with whole cell vaccines. The safety and immunogenicity of similar Shigella conjugates in 4 to 7 years-old children in Israel was demonstrated. But, although the fold rise in anti-LPS was similar in the children, the level of anti-LPS elicited by the conjugates was lower than in adults. We improved the immunogenicity of Shigella conjugates as shown in mice and then in adult humans. Now we apply to evaluate the safety, immunogenicity and efficacy of these improved conjugates in 1 to 4 years-old children in Israel. In addition to monitoring the safety and immunogenicity of the two investigational Shigella vaccines, active surveillance of the vaccines for enteric infections wil be maintained for at lest 2 years to evaluate the effect of vaccination.