ABSTRACT
INTRODUCTION Immunization against infectious diseases is recognized as the most cost-effective method for controlling and eradicating microbial infections (WHO, UNICEF document 1996). However, despite the introduction over the years of both human and animal vaccines against a variety of viral and bacterial pathogens, many diseases remain unconquered. This is due, in part, to problems associated with vaccine delivery, stability, and cost. Other major hurdles to be overcome include stimulating immunity at the most effective site, reducing the need for repeated injections to overcome short-lived immunological memory, and stimulating the necessary CTL responses, and antigenic variation among the causative agents.
