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INTRODUCTION

Vaccines are among the most successful public health interventions of all time. Diseases that once killed thousands of children each year have been virtually eliminated from the United States (Table 3-1). Because vaccines are so effective, many parents and younger physicians have little firsthand experience with the infectious diseases that they prevent. In this context, attention has shifted from concerns of vaccine-preventable diseases to concerns of vaccine safety, both perceived and real.

TABLE 3-1Impact of Vaccines in the Twentieth and Twenty-First Centuries

Figure 3-1 depicts what may occur if the public loses faith in the immunization system. Disease incidence begins to decline when a new vaccine is introduced. If there is loss of confidence in the vaccine among a critical proportion of the population, outbreaks may occur. Continued decrease in disease incidence with potential disease eradication can occur only if public confidence in the vaccine program is restored.

FIGURE 3-1.

Life cycle of an immunization program.

There are several historical examples of what may occur when immunization practices suddenly shift. For instance, the incidence of pertussis was found to be 10–100 times lower in countries that maintained high levels of whole-cell diphtheria–tetanus–pertussis (DTP) vaccination in the 1980s compared with countries with prominent anti-DTP movements.1 In Japan during the mid-1990s, immunizations were rendered optional after the occurrence of rare case reports of aseptic meningitis associated with measles–mumps–rubella (MMR) receipt. Consequently, measles cases and associated harm increased dramatically with more than 100,000 cases and 50–100 deaths attributable to measles per year.2

Even in the United States, where many parents feel that there is little risk for infectious diseases, outbreaks have occurred when individuals are unvaccinated. In 2014, 644 cases of measles were reported in the United States, mostly among unvaccinated individuals—the highest number of cases in two decades. Measles is one of the most contagious vaccine-preventable diseases and is often the first sign of waning immunization rates in a community, since the two-dose MMR series offers near-complete protection. Other diseases, such as mumps and pertussis, persist in the community because of waning immunity. Influenza, the most ...

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