Immunization registry-based recall for a new vaccine.

Background: Immunization recall for specific vaccines may be necessary to "catch up" children with newly available vaccines or recall children after vaccine shortages. The extent to which immunization registry-based recall can increase immunization rates for a new vaccine has not been prospectively studied.

Objective: To assess the efficacy of letter/telephone recall for immunization with pneumococcal conjugate vaccine (PCV7) in an economically disadvantaged urban population.

Design/methods: Randomized controlled trial at an inner-city teaching hospital. Using an immunization registry, we randomly assigned children aged 6 weeks to 22 months unimmunized for PCV7 to an intervention group (n = 610) or a control group (n = 624). The intervention consisted of letter and telephone recall for PCV7 vaccination. Two months after intervention, receipt of 1 or more doses of PCV7 was assessed. Intention-to-treat analysis was used.

Results: We were unable to successfully contact 42.3% of the intervention subjects by mail and telephone. In the intervention group, 23.0% (140 children) received PCV7 within 2 months compared with 20.2% (126 children) in the control group (P = NS). No intervention effect was evident when children were stratified by age. A large proportion of the study population had Medicaid insurance (51.2%) or were uninsured (28.5%), but response to PCV7 recall did not vary by insurance status.

Conclusions: Letter and telephone recall for PCV7 vaccine did not significantly increase the rate of PCV7 immunization in an inner-city teaching hospital serving a disadvantaged population. The effectiveness of recall appears to have been limited by the inability to reach many subjects by mail and telephone.