Immunogenic compositions comprising microparticles with adsorbed toxoid antigen and/or polysaccharide-containing antigen are disclosed. The immunogenic microparticle compositions comprising (a) polymer microparticles comprising a biodegradable polymer； (b) an antigen adsorbed to the microparticles selected from (i) a toxoid antigen, such as a tetanus toxoid, a diphtheria toxoid, or a combination thereof, and/or (ii) a polysaccharide containing antigen, such as a Hib polysaccharide antigen, a Hib conjugate antigen comprising polysaccharide and polypeptide regions, a meningococcal polysaccharide antigen, a meningococcal conjugate antigen comprising polysaccharide and polypeptide regions, a pneumococcal polysaccharide antigen, and a pneumococcal conjugate antigen comprising poysaccharide and polypeptide regions or a combination thereof； and (c) a pharmaceutically acceptable excipient.； The biodegradable polymer can be, for example, a polymer selected from a poly(alpha-hydroxy acid), a polyhydroxy butyric acid, a polycaprolactone, a polyorthoester, a polyanhydride, and a polycyanoacrylate. Also disclosed are methods of immunization against infection by a pathogenic organisms and methods stimulating immune responses, which comprise administering such compositions to host animals. Methods of producing such microparticle compositions are also disclosed which comprise forming a water-in-oil-in-water emulsion that contains water, organic solvent and biodegradable polymer, followed by removal of the organic solvent from the emulsion to form microparticles, after which toxoid and/or polysaccharide containing antigens are adsorbed on the microparticles.
