Drug delivery issues in vaccine development.

Although significant headway has been made in vaccine development, there are several delivery-related issues that must be overcome to advance tomorrow's candidate vaccines. Some of these are in the areas of: single-shot subunit vaccines, therapeutic vaccines for cancer, the use of cytokines as vaccine adjuvants, DNA-based vaccines, and the development of vaccines that provide sterilizing immunity, as might be required for an affective HIV-1 prophylactic vaccine. The hurdles for vaccine advancement in these areas are briefly described.