The deliberate stimulation of an immune response by immunization, or vaccination, has achieved many successes in the two centuries since Jenner’s pioneering experiment. Mass immunization programs have led to the virtual eradication of several diseases that used to be associated with significant morbidity (illness) and mortality (Fig. 1.36). Immunization is considered so safe 100 10 1.0 0.1 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 vaccine inactivated vaccine oral vaccine vaccine measles SSPE 40 30 20 10 0 1940 1950 1960 1970 1980 1990 600 500 400 300 200 100 0 1960 1965 1970 1975 1980 1985 1990 Reported cases per 100,000 population Reported cases per 100,000 population Reported cases per 100,000 population Reported SSPE cases in USA 60 50 40 30 20 10 0 DiphtheriaPolioMeasles
Fig. 1.36 Successful vaccination campaigns. diphtheria, polio, and measles and their consequences have been virtually eliminated in the united States, as shown in these three graphs. SSPe stands for subacute sclerosing panencephalitis, a brain disease that is a late consequence of measles infection in a few patients. When measles was prevented, SSPe disappeared 15–20 years later. However, because these diseases have not been eradicated worldwide, immunization must be maintained in a very high percentage of the population to prevent their reappearance.
and so important that most states in the United States require children to be immunized against up to seven common childhood diseases. Impressive as these accomplishments are, there are still many diseases for which we lack effective vaccines. And even where vaccines for diseases such as measles can be used effectively in developed countries, technical and economic problems can prevent their widespread use in developing countries, where mortality from these diseases is still high.
The tools of modern immunology and molecular biology are being applied to develop new vaccines and improve old ones, and we discuss these advances in Chapter 16. The prospect of controlling these important diseases is tremendously exciting. The guarantee of good health is a critical step toward population control and economic development. At a cost of pennies per person, great hardship and suffering can be alleviated.
Many serious pathogens have resisted efforts to develop vaccines against them, often because they can evade or subvert the protective mechanisms of an adaptive immune response. We examine some of the evasive strategies used by successful pathogens in Chapter 13. The conquest of many of the world’s leading diseases, including malaria and diarrheal diseases (the leading killers of children) as well as the more recent threat from AIDS, depends on a better understanding of the pathogens that cause them and their interactions with the cells of the immune system.
Summary.