The present invention relates to a new vaccine delivery system. In particular, the present invention includes compositions and methods of integrally transformed non-pathogenic, commensal bacteria that can express a nucleic acid molecule of a foreign polypeptide, wherein the nucleic acid molecule that encodes the foreign polypeptide is stably integrated into genomic DNA of the bacteria. The foreign polypeptide includes a vaccine antigen that elicits an immunogenic response, an inhibitor of a pathogen, or an immune booster or modulator.