Despite problems with the acquired immunodeficiency syndrome (AIDS), new microbial agents, malnutrition in one-third of children under the age of five, and decline in income for many parts of Africa, the startling facts, as published by the World Bank in the 1993 World Development Report, show that the past four decades have seen greater improvements in health, greater increases in life expectancy, and greater declines in infant mortality for all regions of the world than in all recorded history before that time. The reason is a grand accumulation of many factors, many health and nonhealth interventions, and the work of countless groups and people. No single intervention can assume the credit.
Having said that, vaccines have been one of the most welcome additions ever seen in international health. A decade ago, measles was perhaps the single most lethal agent in the world, with deaths in the neighborhood of three million a year.