Abstract: Immunogenic compositions are described herein which comprise microparticles that further comprise a biodegradable polymer. The microparticle compositions also comprise a cationic polysaccharide and an immunological species selected from an antigen, an immunological adjuvant and a combination thereof. Also described are methods of making such compositions and methods of administering such compositions. Methods of modulating the release rate of immunological species from microparticles are also described. These methods comprise varying the ratio of the cationic polysaccharide relative to the biodegradable polymer within the microparticles.