Enteric immunization: promises and challenges

Immunization to prevent many intestinal infections is inadequate because most available vaccines are given parenterally, a route that does not effectively stimulate the intestinal immune system. Thus, investigators are pursuing several strategies for achieving enteric protection through oral immunization. The most promising approaches are the incorporation of immunogens into microparticles for protection and enhanced uptake of the immunogen by intestinal lymphoid tissues, the genetic manipulation of microorganisms, and the use of mucosal adjuvants. The achievement of effective oral immunization against intestinal infections could lead to control of serious diarrheal illnesses, which still are a major worldwide health problem.