Catch-up Immunizations at 18 Months of Age: Implications for Individual Practices. A Study from the South Carolina Pediatric Practice RESEARCH Network (SCPPRN)

Background:
Analyses of the National Immunization Survey imply that an additional immunization visit at 18 months could have a substantial effect on immunization rates of individual children.

Objectives:
What effect would one additional immunization visit at 18 months of age have on immunization rates of pediatric practices?

Methods:
We completed retrospective chart reviews of 6 pediatric practices within the SCPPRN on children aged 18 to 30 months of age. Up to date (UTD) status was defined as 4:3:1:3:3:1 (4 DTaP, 3 Polio, 1 Measles, 3 Hib, 3 Hepatitis B: 1 Varicella). Individual practice vaccination rates were determined at age 17 months, 18 months and at assessment. Of those not UTD at 17 months, the percentage of children who could be brought UTD with one visit was calculated for each practice. Calculations were performed with CoCASA 3.3.80.

Results:
There were 2 rural, 2 urban and 2 suburban practices surveyed. The number of charts reviewed at each practice ranged from 117 to 616 (median 382). UTD at 17 months ranged from 14% to 58% (median 31.5%). With one additional visit for children not UTD the range of the practice vaccination rates would improve to 41 to 80% (median 63%). This represents an increase of 18% to 51% (median 28.5%) for individual practices. The observed immunization rate at 18 months ranged from 23% to 64% (median 37%) an increase of 3% to 7% (median 5%) for those practices.

Conclusions:
Practices are not effectively using an 18 month visit for immunization. Practice based interventions targeted at the 18 month visit have the potential to substantially increase individual practice vaccination rates.