Challenges and Successes of Immunization Registry Reminders at Inner-City Practices

Objectives: To assess the effectiveness of two serial registry reminder protocols and the interactive effects of reminders with child characteristics on immunization rates. Methods: At an inner city practice network in New York City we randomized 1662 children aged 6 weeks-15 months due or late for a diphtheria-tetanus-pertussis (DTaP) to 3 groups: continuous reminders (as needed), limited reminders (up to 3) and controls, for 6 months. Reminders were triggered by the hospital registry and immunizations were tracked with both the hospital and city registries. Analyses were based on intention to treat. Results: At randomization, the study groups were comparable (9.2 months of age, 77% Latino, 86% Medicaid, 49.3% up-to date). A quarter of the children were sent false reminders, 15% had incorrect contact information, and 15% had missed opportunities for vaccination. In the univariate analysis, reminders improved coverage rates, but only for the children sent continuous reminders (51.2% vs. 44.9% controls, p < .01). Multivariate analysis showed reminders had no independent effect on immunization outcomes. Age, up-to-date and Medicaid status at randomization were strong predictors of a child receiving any subsequent immunization. However, reminders interacted synergistically with Medicaid to increase the likelihood of receiving an immunization. Conclusion: At an inner city practice network, registry reminders were not effective at improving immunization outcomes due to major system barriers. Immunization registries are powerful vehicles for identifying children in need of immunizations and generating reminders but system challenges must be addressed if this promise is to be achieved in inner city practices.