Clusters of Nonmedical Exemptions to Vaccination in Illinois K–12 Schools

Abstract

Vaccination rates in Illinois schools are decreasing as more parents opt for nonmedical exemptions (NMEs). At the local scale, higher levels of exemptions affect herd immunity levels. Few studies have previously conducted or proposed methods to conduct local-scale spatial and temporal cluster pattern analysis. This study used vaccination exemption data from the Illinois School Board of Education’s annual Immunization School Survey for the 2003–2004 and 2013–2014 academic years. The Getis–Ord General G statistic was used to identify cluster detection by individual vaccine at the school level. The Getis–Ord Gi* statistic was used with two different parameter models to identify hot and cold spots. This study found that NMEs are highly clustered. More clusters of high and low NMEs were identified for the 2013–2014 academic year than for 2003–2004. The percentages of schools that were neither hot nor cold averaged 94.0 percent for the 2003–2004 school year and 78.7 percent for the 2013–2014 school year. NME rates in Illinois are rising. The increase in hot and cold spots is evidence that the polarity of vaccination choice is growing. As vaccination exemption rates continue to polarize U.S. society, it is essential for public health efforts to monitor and conduct local-level studies. Key Words: antivaccination, hot spot analysis, medical geography, nonmedical exemption, spatial statistics.

在伊利诺州, 由于越来越多的父母选择非医疗豁免（NMEs), 学校的疫苗接种率正逐渐降低中。在地方层级, 较高程度的豁免影响了群体免疫的程度。过往鲜少有地方尺度时空集群模式分析之研究, 抑或对此提出研究方法。本研究运用伊利诺州学校教育委员会在2003-2004学年与2013-2014学年的年度学校免疫调查之疫苗豁免数据, 运用高／低聚类统计来指认学校层级各疫苗的群集侦测。高／低聚类统计同时与两大不同的参数模型进行使用, 以指认热点和冷点。本研究发现NMEs高度群集。2013-2014学年较2003-2004学年而言, 指认出更多的高与低NMEs之群集。非热点亦非冷点的学校比率, 在2003-2004学年平均为百分之九十四, 在2013-2014学年则为百分之七十八点七。伊利诺州的NME比率正逐渐上升。热点与冷点的增加, 证明了疫苗选择的两极化正在扩大。随着疫苗豁免率持续极化美国社会, 有关公共健康的努力, 必须监测并进行地方层级的研究。关键词：反对疫苗接种, 热点分析, 医疗地理学, 非医疗豁免, 空间统计。

Las tasas de vacunación en las escuelas de Illinois están decreciendo a medida que más padres optan por exenciones no médicas (NMEs). A escala local, los niveles más altos de exenciones afectan los niveles de inmunidad en masa. Pocos estudios han conducido o propuesto con anterioridad métodos para efectuar a escala local análisis de patrones de aglomeración espacial y temporal. Este estudio usa datos de exención de vacunación del Estudio Anual de Inmunización Escolar de la Junta Escolar de Educación de Illinois, correspondiente a los años académicos de 2003–2004 y 2013–2014. Para identificar la detección de aglomeraciones por matrícula individual a nivel escolar se usó la estadística Getis-Ord G General. Se usó la estadística Getis–Ord Gi* con dos modelos de parámetros diferentes para identificar puntos calientes y fríos. Este estudio descubrió que las NMEs están altamente aglomeradas. Se identificaron más aglomeraciones altas y bajas de NMEs para el año académico 2013–2014 que para el 2003–2004. Los porcentajes de escuelas que no fueron ni calientes ni frías promediaron 94.0 por ciento para el año escolar 2003–2004 y 78.7 por ciento para el año escolar 2013–2014. Las tasas de NME en Illinois se están elevando. El aumento de puntos calientes y fríos evidencia que la polaridad para elegir la vacunación está creciendo. En la medida en que las tasas de exención de vacunación continúen polarizando la sociedad norteamericana, es esencial para los esfuerzos de salud pública monitorear y realizar estudios a nivel local.

MOTS CLÉS:

• Palabras clave: análisis de puntos calientes
• antivacunación
• exención no médica
• geografía médica

Acknowledgments

I am grateful to Dr. Deryck Holdsworth, Dr. Anthony Robinson, and Dr. Roger Downs for their assistance as advisors and mentors throughout this research project. Thanks to the editor and reviewers for useful feedback throughout the publication process.

Notes

1 The 2003–2004 and 2013–2014 academic years fell under the exemption guidance established in 1979 where a guardian was required to write a statement objecting to vaccination (Illinois 81st General Assembly 1979). In 2015 Illinois updated its definition of religious exemptions, adding that “general philosophical or moral reluctance … does not provide a sufficient basis for an exception” (Illinois Public Act 099–0249 2015). Starting with the 2016–2017 academic year, parents are required to have a health provider’s signature in addition to a personal exemption statement (ISBE 2015).

2 The hot spot locations for polio, mumps, rubella, and DTP are similar to the locations of the measles hot spots in Figures 1 and 2.

Additional information

Notes on contributors

Elizabeth A. Dzwonczyk

ELIZABETH A. DZWONCZYK is an Assistant Professor of Geography in the Department of Geography & Environmental Engineering, United States Military Academy, West Point, NY 10996. E-mail: [email protected]. Her research interests include vaccination, exploring geographic patterns of health and disease using GIS, and geography education.