Background: Healthcare systems have been challenged to ensure the timely administration of immunizations. Immunization registries have been proposed to improve the accuracy and completeness of immunization information and to promote effective practice.
Methods: Comparison of randomly selected samples from two birth cohorts (1993 and 1998) from Denver Health Medical Center. Chart review and immunization registry information for these groups were compared; a composite immunization was recorded and up-to-date (UTD) status established. Registry data were compared with this composite using a sensitivity measure to assess completeness and accuracy.
Results: Among 818 children in the 1993 cohort and 1043 children in the 1998 cohort, there were 6386 and 6886 valid immunizations, respectively. The registry recorded 71.4% and 97.7% of these for the 1993 and 1998 cohorts, respectively (p <0.001). The apparent UTD rate, as measured with registry data alone, improved from 37% to 79% between the two time frames (p <0.001). Composite UTD status was 83.1% and 78.9% (1993 vs 1998, respectively). Accurate registry-defined UTD status improved from 44.4% to 100% between the two intervals.
Conclusions: Immunization registry accuracy improved dramatically for recorded immunizations and UTD status. However, after 3 years of registry use, the overall proportion of children who were UTD had not significantly improved. The mere presence of a registry does not ensure more complete vaccination coverage. Other registry-based strategies, including use of the data for reminder, recall, and audit, may further improve immunization coverage.