Immunization Coverage in a Population-Based Sample of Maryland Children

Objective: To describe the vaccination coverage of a population-based sample of Maryland children. Design: Historical cohort study using stratified cluster sampling. Strata were formed from five state regions and public and private schools within each region. Setting: Random sample of elementary schools in Maryland. Subjects: Immunization records were obtained for a randomly selected cohort of 1938 first-grade children in Maryland. Outcome Measures: Age of completion of recommended childhood vaccines and proportion of vaccines given simultaneously. Results: By first grade, 95.2% of the sample of Maryland children were documented to have received at least four doses of the diphtheria and tetanus toxoids and pertussis (DTP) vaccine, three doses of oral poliovirus (OPV) vaccine, and one dose of measles-mumps-rubella (MMR) vaccine. However, only 54.8% of children surveyed had achieved this level of immunization by 24 months of age. For children whose immunizations were up to date on their first birthday (78.7% of children surveyed), vaccine providers failed to administer one dose of DTP, OPV, and MMR vaccines to 30% of these children during the second year of life. Only 16.2% (n=313) of children sampled received an MMR vaccination simultaneously with any dose of DTP or OPV vaccine. Conclusions: This study shows that while immunization levels are very high at school entry, there are serious delays in vaccine administration before school entry. These delays are observed regardless of whether children are in public or private schools or attend school in an urban, suburban, or rural area. Physicians and health care providers could play an important role in age-appropriate vaccination by administering vaccines simultaneously. (Arch Pediatr Adolesc Med. 1994;148:350-356)