Causes and Epidemiology of Diseases Prevented by Vaccines Used in National Immunization Programs

Vaccination against childhood communicable diseases through the Expanded Program on Immunization (EPI) is one of the most cost-effective public health interventions available (UNICEF 2002; World Bank 1993). By reducing mortality and morbidity, vaccination can contribute substantially to achieving the Millennium Development Goal of reducing the mortality rate among children under five by two-thirds between 1990 and 2015. Accelerated research into the development of new vaccines has been made possible in part by innovative publicprivate partnerships, such as the Global Alliance for Vaccines and Immunization (GAVI). GAVI focuses on expanding access by immunization programs in developing countries to new and underused vaccines, such as those for hepatitis B and Haemophilus influenzae type B (Hib). These newer, more expensive vaccines are challenging previous notions of the cost-effectiveness of immunization. Analyses of their costs and cost-effectiveness are particularly important because of the need to determine the level of resources required in the future to improve immunization programs, to cover the costs of new vaccines, and to allocate scarce public and external resources available for immunization in the most optimal manner. This chapter analyzes the costs and cost-effectiveness of scaling up the EPI and introducing selected new vaccines into the program. It also summarizes the epidemiology of diseases preventable through immunization and estimates the disease burden with and without immunization programs. In addition, the chapter discusses the organization, delivery, and financing of immunization programs and highlights future prospects and areas for further study. Several areas overlap with other chapters. For example, the vaccines that prevent measles, tuberculosis, diphtheria, pertussis, Hib, and Neisseria meningitis prevent respiratory diseases. Some vaccines, such as those against measles and pertussis, prevent diseases that cause or contribute to malnutrition. Chapter 16 provides an in-depth review of tuberculosis and a discussion of the potential impact of bacillus Calmette-Guérin (BCG) vaccines. This chapter also does not discuss some new vaccines, including conjugate Streptococcus pneumoniae, influenza, typhoid fever, and rotavirus, because other chapters deal with those diseases and vaccines. Vaccines to prevent mumps and varicella that are routinely used in some developed countries are not included in most vaccination programs in developing countries. Other interventions that can reduce the burden of vaccine-preventable diseases and are not covered in this chapter include clean umbilical cord care to reduce the incidence of neonatal tetanus, vitamin A therapy to reduce the case-fatality rate (CFR) from measles, and intensive clinical care that can reduce the mortality associated with most of the vaccine-preventable diseases.