Vaccination remains the most valuable tool for prevention of infectious diseases. Through the Expanded Program on Immunization, diseases such as polio and tetanus are in decline worldwide, and in some cases even close to being eliminated. Nevertheless, many existing vaccines are not as effective as desired. This is especially true for the elderly. In addition, there are many diseases for which vaccines are still not available.
The basic conceptual idea of vaccination has remained unchanged since its initial implementation over 200 years ago: attenuated or inactivated pathogens or subcellular components from them are introduced to mimic natural immunity to infections with the hope to stimulate a protective immune response. The current trend of exploiting well-defined purified antigens for the generation of subunit vaccines poses the problem of their poor immunogenicity, since whole cell crude preparations contain many products with built in immune stimulatory activity. This raises the critical need of incorporating adjuvants in the formulation. Although adjuvants have been used for more than 70 years, until now only a handful has been licensed for human use. Thus, the development of safe adjuvants which are able to promote proper immune responses remains a major challenge in vaccinology.