ABSTRACT
INTRODUCTION Since Jenner’s application of “vaccination” to protect humans from smallpox in 1796, countless lives were saved by passive and active immunization therapy. Today a variety of vaccines is commercially available, mostly used in repeated immunization schemes to induce antibody titers adequate for protection (Fudenberg et al., 1978). Frequently, three applications are necessary to increase or “booster” the antibody titers or cellular responses sufficiently for protection. In developing countries, where access to the health care system is poor, patient compliance for vaccination schemes requiring repeated immunizations has been notoriously low. It would be desirable to offer to this patient population a vaccine delivery system which induces a protective immune response after one single administration of the antigen (Aguado, 1993).
