![[ Visit Client Website ]](images/banner.jpg)
BACKGROUND: Children with exemptions from immunizations are at increased risk of contracting and transmitting vaccine-preventable diseases such as pertussis, a highly contagious respiratory disease known to be fatal among infants and the elderly. Despite high vaccination coverage levels in Texas, pockets with high rates of exemptions can occur that may potentially increase the risk of transmission of vaccine preventable diseases. The number of children with conscientious objections ( COs) to immunizations at Texas public and private schools has increased from 2,314 during the 2003-04 school year to 32,616 in the 2012-13 school year. Peak year incidence of pertussis disease has increased from 9.7 per 100,000 in 2005 to 14.8 per 100,000 in 2013. Analysis was conducted to determine if there is an association between reported cases of pertussis disease in a zip code and COs requested in a zip code for the years 2011-2013 in Texas.
METHODS: Using Zip Code Tabulation Area (ZCTA) data, pertussis incidence rates and rates for individuals requesting COs were calculated for each zip code. ArcGIS, version 10.2, was used for creating geographic analysis layers and performing hot spot analysis. SAS, version 9.3, was used to calculate Spearman’s rank correlation coefficients for both the association between case and CO counts and for association between pertussis incidence and rates for individuals whom a CO was requested.
RESULTS: Spearman’s rank correlation coefficients for individuals for whom a CO was requested and pertussis cases ages 0-19 by zip code for 2011, 2012, and 2013 were 0.44, 0.56, and 0.64 respectively. The correlation coefficient for pertussis incidence in persons 0-19 years of age and the rate of individuals for whom a CO was requested for 2011, 2012, and 2013 was 0.28, 0.28, and 0.35 respectively. Hot Spot Analysis tool was used to identify pertussis and CO clusters.
CONCLUSIONS: The results of the study indicate a moderate positive association between pertussis incidence rates and rates of individuals for whom COs were requested for persons 0-19 years of age. There is a strong positive association between the number of pertussis cases and the number of individuals for whom COs were requested by zip code. Clustering of COs reduces the vaccination coverage level that is necessary to maintain herd immunity and protect populations at risk for serious complications to vaccine preventable diseases.