Introducing new vaccines into developing countries: obstacles, opportunities and complexities.

Infectious diseases are thought to account for nearly 25% of all deaths worldwide, and extract a disproportionate toll in developing countries. Moreover, infectious diseases are now appreciated to be major causes of the poverty and economic underdevelopment that characterize the world's poorest countries. Development and deployment of new vaccines to prevent infectious diseases in developing countries have therefore become high priorities in the global health agenda.