1. Krista Rietberg, MPH Charla DeBolt, RN, MPH Nita Heimann, MN, MPH David Bibus, MPH Jeffrey S. Duchin, MD Public Health-Seattle & King County School Exemption Data and Geocoding as Tools for Assessing Relationships of Pertussis Clusters to High Immunization Exemption Rates

2. Objective To evaluate the relationship between school immunization exemption rates and incidence of pertussis disease in the community Public Health Seattle & King County

3. Pertussis on Vashon Island Incidence of Pertussis 1998 (cases/100,0000) 112.7 Vashon Island 9.4 King County overall Public Health Seattle & King County

4. Vashon Island

5. The Vashon Island Example Only one public school district on the island –one elementary, middle, and high school Public Health Seattle & King County

6. The Vashon Island Example School Immunization Exemption Rates Public Health Seattle & King County

7. The Study Question Is there an association between incidence of pertussis disease and high immunization exemption rates in other parts of King County? Public Health Seattle & King County

8. Immunization Exemptions in Washington State (background) Students must provide signed proof of required immunizations for attendance in school Washington State permits medical, religious, or personal/philosophical exemptions Public Health Seattle & King County

9. Pertussis in King County Dramatic increase in pertussis cases began in 1995 Highest rates since early 1980’s 48 reported cases in 1994 263 reported cases in 1995 458 reported cases in 1999 Public Health Seattle & King County

10. Pertussis Incidence in King County and Washington State

11. Pertussis immunization status of 264 King County pertussis cases under 18 years of age 1999

12. Methods Pertussis case residence and location of schools were geo-coded by census block group using Geo-Vista Maps were created using Arc View Maps were overlaid on existing maps of the 17 school districts in King County Public Health Seattle & King County

19. Pertussis “Hot Spots” Public Health Seattle & King County

20. Results Several school districts with high pertussis rates School districts with exemption rates significantly higher than the county average had higher rates of pertussis (Vashon Island) Public Health Seattle & King County

21. Conclusions On Vashon Island there appears to be an association between high immunization exemption rates and incidence of pertussis This association was not seen to the same extent in other school districts Cases of pertussis appear to cluster in areas with high immunization exemption rates Public Health Seattle & King County

22. Limitations of School Exemption Data Lack of immunization record validation Schools in Washington state use exemption status for compliance Approximately 26% of schools did not report exemption data for 99-00 school year Children may attend school in a different district than where they live Public Health Seattle & King County

23. Limitations of GIS/Geo Vista Time consuming –Approximately 10% of cases coded by hand When a new map is created the geo-code is randomized so clusters may or may not be apparent Census block groups do not match school district lines exactly Public Health Seattle & King County

24. Discussion Need for immunization record validation Need for improved reporting by schools –Educating schools about the importance of accurate immunization records Importance of accurate and complete case reporting Public Health Seattle & King County

25. Discussion Elevated immunization exemption rates correlate with number of susceptible children in the school environment Elevated exemption rates suggests a relationship to increased pertussis rates Exemption rates may not be the only factor driving up pertussis rates