Abstract

Immunization against infectious diseases has saved innumerable lives and contributed to today's increased life expectancy. In spite of these impressive results, there is still considerable potential for improved vaccines. New strategies to achieve safe and effective immunization are under investigation. Many vaccination guidelines call for multiple dosing schedules. Reduction of injection frequency, by having controlled release, peroral or nasal vaccine delivery systems could lead to better immunological protection of the population and might facilitate in eradication of some infectious pathogens. Some aspects of safety are closely related to the route of administration, such as granuloma formation or allergic reaction at the injection site and storage conditions. Serious failures of smallpox and measles immunizations have resulted from inadequate refrigeration. New vaccine delivery systems have shown to possess greater effectiveness, improved adjuvanticity, in vitro and in vivo stabilization of antigens, safety from risk of infections and side effects. Furthermore, results obtained by delivering the new subunit vaccines against diseases such as Hepatitis B, HIV, malaria by novel delivery systems have shown encouraging results. Biodegradable micropheres made up of PLGA, liposomes, nanoparticles, immunostimulating complexes and nonionic surfactant vesicles have been reviewed here and these have found to be promising modes of vaccine delivery.