Learning Objectives for this Presentation:
By the end of the presentation, participants will be able to
Understand the value in a high-school area based approach to identifying pockets of high immunization exemption rates and associated common community risk factors.


Background:
In Oregon, exemptions to school immunization requirements are clustered locally. Exemption data in Oregon is collected for individual schools. A systematic approach used to aggregate individual school data into larger areas would be useful to link with population data. This linked data could answer whether community level features can be used to predict exemption rates, or whether factors unique to individual exemptors are dominant.

Objectives:
To present a method for surveillance of exemptions across communities, based upon school level information.

Methods:
School level data on enrollment and exemptions was collected for Oregon public schools for grades K-12 for the 04/05 school year. Data was aggregated by grade schools; then rolled up into high school catchment areas. Overall 228 high-school based areas (HBAs) were identified, representing 1,238 schools in total. HBAs were then categorized as high, medium, or low based on their exemption rate. Each HBA was linked to census areas. Rates on education, income, population, race, providers, and alternative births, were calculated for each HBA.

Results:
Within high rate HBAs, 76% of individual schools had a high exemption rate, as contrasted to 11% of schools in non-high rate HBAs, with RR= 6.9, (5.7 to 8.4). The strongest predictors of high exemption rates on a local level were the presence of alternative providers, and the rate of non-hospital births. Education and income levels were also significant, though of lower effect.

Conclusions:
HBAs are a good unit for aggregation for defining a community. An ecological analysis of HBA exemption rates and population risk factors is a viable method of identifying communities at risk for high exemption rates.