Evaluation of a follow-up system in a county health department's immunization clinic.

We designed a pilot follow-up system using two mailed reminders and evaluated it for use in the immunization clinic of a relatively large county health department in Washington State. Compliance with the recommended interval for DTP immunizations increased by 33.9% in the group of children receiving two postcard reminders compared to the control group. Over half of the respondents (52%) in the control group and 28% in the intervention group reported that transportation barriers and clinic problems prevented their return.