To maintain a vaccine center with broad capabilities to evaluate prophylactic and therapeutic agents against human pathogens other than AIDS. To evaluate vaccine candidates in a critical and objective fashion for safety, immunogenicity, transmissibility, stability and efficacy, we will put a special emphasis on comparative trials of different vaccines against a common agent. To study the biology of microbial agents targeted for vaccine development in order to enhance understanding of attenuation and virulence mechanisms. To examine in detail the host response in man and animal systems to a particular vaccine in so far as it will help understand the mechanism(s) of protective efficacy of the vaccine in question and/or the basic pathogenesis of the disease for which prevention is sought. To contribute to the direction and focus that vaccine development should pursue at a national and international level.