"IDEAL" vaccines for resource poor settings.

In developing countries, immunization delivery would be more efficient, safer and economical if all vaccines could elicit long-term protection following needle-free administration of just a single dose and without need for a cold chain, and if immunization left an indelible (e.g., serologic) marker that would identify immunized persons. A few existing vaccines (e.g., yellow fever, measles) confer long-term protection following a single dose. To accomplish the same with less immunogenic live vaccines and with non-living antigens, potent (parenteral and mucosal) adjuvants are required. Emerging knowledge of how the innate immune system modulates adaptive immune responses is guiding development of modern adjuvants that can markedly enhance immune responses to vaccines by selective stimulation of components of the innate immune system. Needle-free immunization can be accomplished by administering vaccines via mucosal (oral or nasal) or transcutaneous routes or by parenteral injection using needle-free injection devices. Technologies such as vitrification (treatment with trehalose followed by drying) render vaccines resistant to temperature extremes. Ideally, immunization would lead to a biomarker such as a specific vaccine-derived antibody that allows differentiation of successfully immunized persons from susceptibles.