vaccine-preventable illnesses across the country. For example, measles and pertussis outbreaks have occurred in recent years in geographic areas with higher concentrations of unimmunized children (Felkin et al., 2000). States with easy procedures for granting exemptions were associated with a 90 percent higher incidence of pertussis in 2004 (Omer et al., 2006). Some vaccine-preventable diseases can be fatal and have caused morbidity and mortality in infants and people with compromised immune systems. The impacts on disease prevention that vaccines have had in the United States are illustrated in Table 1-1.

Vaccinations—like all medical procedures—are neither 100 percent free of risk nor 100 percent effective. Vaccines, in rare cases, can cause illness. Most children who experience an adverse reaction to immunization have a preexisting susceptibility. Some predispositions may be detectable prior to vaccination; others, at least with current technology and practice, are not (IOM, 2012, p. 82). The U.S. Department of Health and Human Services (HHS), through its agencies responsible for vaccine safety, supports such research and surveillance, including studies addressing concerns and fears over the current childhood immunization schedule. The system in the United States designed to ensure vaccine safety is detailed in Chapter 3. While immunization may be one of the greatest achievements in public health, the complex interactions among populations, health care systems,

TABLE 1-1 Comparison of Pre-Vaccine Annual Incidence and Current Morbidity for Vaccine-Preventable Diseases

Disease 20th Century Annual Morbidity (No. of Cases)a No. of Cases Reported in 2011b Percent Decrease
Congenital rubella syndrome 152 0 100
Diphtheria 21,053 0 100
Haemophilus influenzae 20,000c 14d >99
(<5 years of age)
Measles 530,217 220 >99
Mumps 162,344 404 >99
Pertussis 200,752 18,719 89
Polio (paralytic) 16,316 0 100
Rubella 47,745 4 >99
Smallpox 29,005 0 100
Tetanus 580 36 98

a SOURCE: Roush et al., 2007.

b SOURCE: CDC, 2012a.

c Estimated.

d Haemophilus influenzae type b among children <5 years of age.



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