Deficiencies in current childhood immunization indicators

Objective. To investigate "up-to-date" and "age-appropriate" indicators of preschool vaccination status and their implications for vaccination policy. Methods. The authors analyzed medical records data from the Baltimore Immun ization Study for 525 2-year-olds born from August 1988 through March 1989 to mothers living in low-income Census tracts of the city of Baltimore. Results. While only 54% of 24-month-old children were up-to-date for the pr imary series. indicators of up-to-date coverage were consistently higher, b y 37 or more percentage points, than corresponding age-appropriate indicato rs. Almost 80% of children who failed to receive the first dose of DTP or O PV age-appropriately failed to be up-to-date by 24 months of age for the pr imary series. Conclusions, Age-appropriate immunization indicators more accurately reflec t adequacy of protection for preschoolers than up-to-date indicators at bot h the individual and population levels. Age-appropriate receipt of the firs t dose of DTP should be monitored to identify children likely to be underim munized. Age-appropriate indicators should also be incorporated as Vaccinat ion coverage estimators in population-based surveys and as quality of care indicators for managed care organizations, These changes would require accu rate dates for each Vaccination and support the need to develop population- based registries.