Disclosed are immunogenic conjugates and therapeutic compositions that include such immunogenic conjugates. Also disclosed are methods of treating and/or inhibiting an Shigella sonnei infection. The disclosed immunogenic conjugates have the general structure: Pr—Sr—O—N═C-Kdo-OS wherein Pr is a carrier protein, Sr is an optional spacer moiety, Kdo is an 3-deoxy-D-manno-octulosonic acid or a derivative thereof, and OS is an oligosaccharide or polysaccharide obtained from S. sonnei. In specific examples, the immunogenic conjugates include the core oligosaccharide obtained from S. sonnei having the structure: wherein R is between 1 and 10 disaccharide repeat units. In specific examples, the disaccharide repeat unit included in the immunogenic conjugate has the structure: α-L-AltNAcA-3-β-FucNAc4N-4-.