One hundred Egyptian village children were immunized with 1.0 ml. of a Shigella flexneri 3 vaccine, given in three divided doses of 0.3 ml., 0.3 ml. and 0.4 ml. at weekly intervals. A similar group of unvaccinated children were observed as controls. During a six month observation period following vaccination, 25 (26.8 per cent) of the children who received the vaccine were found to be infected with Shig. flexneri 3 organisms as compared with 18 (20.4 per cent) of the children in the control group. The number of infections with other Shigella organisms, and the number of episodes of diarrheal disease, was approximately the same in both groups of children.
Immunization with a Shigella flexneri 3 vaccine was not effective in preventing Shigella flexneri 3 infections, or diarrheal disease associated with these organisms, in a group of Egyptian village children living in a highly endemic environment.