Immunization. Past successes, future challenges.

Global eradication of smallpox, elimination of poliomyelitis in the Western Hemisphere, and a 90% decrease in Haemophilus influenzae meningitis in the Western Hemisphere mark some of the achievements of immunization programs around the world. Yet many serious problems continue to exist, particularly in the developing world. Advances in biotechnology and the renewed interest by industry, governments, and the World Health Organization in vaccine development and delivery in the field provide an exciting prospect for major advances in immunization in the next few decades.