Interview Survey (NHIS) found that 82 percent of 2-year-olds had received a measles vaccination, but only 53 percent had received the recommended third dose of polio vaccine. Recently published data from the 1992 NHIS show a similar measles vaccination rate and 72 percent with three doses of polio vaccine (CDC, 1994a). CDC notes that the improvement in coverage against polio may reflect the success of immunization efforts but that changes in survey methodology between 1991 and 1992 also may be a factor.2
Immunization levels among preschool children have long fallen short of the desired target of 90 percent (Stehr-Green et al., 1993b), but serious outbreaks of vaccine-preventable diseases have led to increased awareness of the problem. Delayed immunization of preschool children threatens the health of children of all racial, ethnic, and socioeconomic groups. Low immunization rates for African-American, Hispanic, and other minority children and children living in poverty must be improved but are not the only problem. Data for 1992 show that 75 percent of the 2-year-olds not immunized against measles were white, and 72 percent were in families with incomes at or above the poverty line (CDC, 1994a).
No easily delineated system of primary care exists in the United States. For immunization and other services, providers in the public and private sectors deliver varying sets of services, under diverse systems of compensation, to which families have differing degrees of access. For immunization in particular, no consensus seems to exist as to how responsibility for ensuring that children receive the appropriate care should be shared among parents, providers, payers, and health departments. This can result in gaps in children's care.
In considering the factors that contribute to delayed immunization of preschool children, the workshop focused on those that lie in the organization and delivery of immunization and other health care services and those that lie in families' incomplete or inaccurate understanding of children's health care needs. Other factors—poverty, homelessness, and changing family structure, for example—are much broader in scope than immunization services or health care per se. Addressing these issues was well beyond the scope of the workshop, but their impact on children and children's health care must be acknowledged and was touched on during the workshop.
In the 1991 survey, respondents were asked for the exact ages at which a child received a vaccine. In the 1992 survey, however, parental reports that children had received vaccines did not require information on the age at which the child was immunized. In 1994, provider records will be checked to establish the immunization status of 2-year-olds (specifically, any child who is 19 to 35 months of age) (CDC, 1994a).