BACKGROUND:
Prior to the 2003 US introduction of DTaP-HepB-IPV, 16-20 vaccine injections were required by age 2 years for schedule compliance. Because clinicians and parents dislike administration of too many injections at single visits, some vaccine doses are deferred. These missed opportunities result in some children falling at least temporarily behind the recommended schedule, yet the associated effects on coverage rates are not well understood. The degree to which DTaP-HepB-IPV will reduce missed opportunities and improve coverage rates is unknown.

OBJECTIVE:
Our objectives were to estimate DTaP-HepB-IPV effects on immunization coverage rates, number of vaccine injections, and vaccination costs.

METHOD:
A model was developed and applied to medical records of 775 children born in mid-2001 receiving routine care at 32 private pediatrics centers. DTaP-HepB-IPV use was predicted by applying decision rules to selectively substitute it for component vaccines, in compliance with ACIP minimum age and time interval criteria. The model considered effects of DTaP-HepB-IPV on use of HepB at age <6 weeks, and HepB, Hib-HepB, Hib, DTaP, and IPV at age 6 weeks to 2 years. Coverage rates were compared using McNemar's test for matched pairs, and number of injections using paired t-test.

RESULT:
DTaP-HepB-IPV would increase coverage rates at age 2 years for ³3 HepB doses (95.2% vs. 91.7%, p<.001), ³3 DTaP doses (96.4% vs. 95.6%, p=.02), and ³3 IPV doses (96.3% vs. 90.7%, p<.001). Children modeled to receive the combination vaccine were estimated to receive fewer injections by age 2 years (17.3 vs. 14.6, p<.001), and at reduced cost ($698 vs. $681).

CONCLUSION:
DTaP-HepB-IPV use is estimated to improve coverage rates while reducing vaccine injections and vaccination costs.

LEARNING OBJECTIVES:
To understand how use of combination vaccines may increase coverage rates.