BACKGROUND:
Rhode Island's Haemophilus influenzae type b (Hib) immunization coverage levels have been declining on the National Immunization Survey (NIS) since the state began its transition from a 4-dose to a 3-dose immunization schedule. It is believed this decline is the result of the NIS count methodology rather than an actual decline in coverage. The NIS measures Hib series completeness based on receipt of a minimum of 3 doses of Hib vaccine, but it neglects to account for minimum dose ages and required spacing between doses, and it does not differentiate between children on 4-dose and 3-dose immunization schedules. This could potentially bias the results in favor of 4-dose immunization schedule states, as well as overestimate the rates of Hib vaccination coverage.

OBJECTIVE:
To determine if Hib dose schedule influences Hib immunization coverage rates on the National Immunization Survey.

METHOD:
A study sample was chosen that was consistent with the 2003 NIS to facilitate comparisons with national and state level data. The sample, immunization histories, and other child characteristics were obtained from KIDSNET, Rhode Island's immunization registry database. Hib immunization coverage is currently being assessed using three different methods. The results from these assessments will then be compared to the NIS count methodology.

RESULT:
KIDSNET data reflects NIS data when using the NIS count methodology. It is expected that these rates will differ with the new methodologies.

CONCLUSION:
The NIS count methodology does not adequately assess Hib immunization coverage. It is important to consider minimum dose ages and required dose intervals, as well as varying dose schedules, in order to assure children are adequately protected against vaccine preventable diseases.

LEARNING OBJECTIVES:
Participants will learn:
1. The impact of a 3-dose vs. a 4-dose immunization schedule on immunization coverage rates on the NIS
2. The value of implementing better immunization assessment methods on the NIS