[Controlled release antigen from the injection site--new model for a single-shot vaccination?].

Continuously increasing number of available vaccines and a wide use of mass vaccination campaigns lead to the development of simpler methods of vaccine delivery. There is the WHO-sponsored project, including several scientific groups, which aims to reduce the number of repeated administrations of vaccines required for long-term protection and to obviate the need for booster immunization. Such a task may be achieved by the use of controlled-release parenteral systems. One such delivery system comprises microspheres constructed from biodegradable, biocompatible polymers based on poly lactic/glycolic acid. Recent developments of a single-shot tetanus toxoid, encapsulated in the biodegradable polymeric microspheres or microcapsules are reviewed. There are promising advances in the WHO-sponsored project. However, further efforts are needed to elaborate an affective late release of antigen and to obtain a strong booster effect in vaccinated animals.