Learning Objectives for this Presentation:
By the end of the presentation participants will be able to understand the limitations of commonly used data sources in measuring immunization coverage for American Indian/Alaska Native (AI/AN) children.

Background:
Current data sources are insufficient for measuring immunization coverage for AI/AN children.

Objectives:
Compare methodologies of the National Immunization Survey (NIS) and the Indian Health Service (IHS) immunization reporting system to explain observed differences in immunization coverage estimates for AI/AN children.

Methods:
The NIS is a random digit dial telephone survey of children 19 – 35 months of age. The IHS immunization data is collected quarterly from all IHS and participating tribal facilities for AI/AN children 3 – 27 months seen at those facilities. IHS coverage estimates were calculated for children 19 – 27 months. Annual IHS coverage estimates were derived from an average of the 4 quarters in each year. We compared 2001-2004 NIS and IHS coverage estimates of the 4:3:1:3:3 immunization series for AI/AN children.

Results:
The average quarterly sample of AI/AN in the IHS data was 10,751 compared to an average annual sample of 290 for the NIS. NIS and IHS coverage levels were as follows: 2001: 72.7% (+ 8.6) vs. 83.4%; 2003: 74.9% (+7.8) vs. 80.2%; 2004: 73.0% (+ 8.7) vs. 79.2%. For 2002, the NIS did not report data for AI/AN children due to insufficient sample size.

Conclusions:
The IHS data and NIS data report different levels of coverage for AI/AN children, with the IHS data reporting higher coverage than the NIS data. Observed differences in coverage are likely related to differences in survey methodologies. Because the NIS is limited by small sample sizes for AI/AN children, the NIS may not be the best tool to evaluate immunization coverage for the AI/AN population.