BACKGROUND: Demographic characteristics such as household income, race, and education have been shown to impact vaccination coverage and exemption rates among school-aged children. Immunization programs currently report state-aggregated kindergarten vaccination coverage and exemption data to the Centers for Disease Control and Prevention (CDC), but do not assess information related to demographic characteristics. The objective of this study was to use geographic information system (GIS) software to assess correlations between household income and vaccination coverage among kindergartners in Arizona.
METHODS: School-level kindergarten vaccination coverage and exemption assessment data for the 2014-15 school year was matched with National Center for Education Statistics (NCES) school attendance boundary areas for 687 Arizona public schools. Census block-level estimates for 2014 median household income were spatially joined to the school assessment data by calculating the mean of the median household income values among all Census blocks within each school attendance boundary. Correlation coefficients were calculated to assess statistical relationships between household income and the percent of kindergartners up to date (UTD) or exempt by vaccine under state requirements (diphtheria, tetanus, and acellular pertussis [DTaP], Polio, Measles, mumps and rubella [MMR], Hepatitis B, and Varicella).
RESULTS: Among 687 Arizona public schools during the 2014-15 school year, mean median household income was negatively correlated with the percent of kindergartners UTD for each of the state’s required vaccines (p<0.0001 for all): DTaP (r= -0.25); Polio (r=-0.28); MMR (r=-0.28); Hepatitis B (r=-0.32); and Varicella (r=-0.27). Household income was positively correlated with the percent of kindergartners exempt from each vaccine (p<0.0001 for all): DTaP (r= 0.36); Polio (r=0.37); MMR (r=0.38); Hepatitis B (r=0.36); and Varicella (r=0.32).
CONCLUSIONS: High household income was associated with lower vaccination coverage and higher exemption rates among public school kindergartners in Arizona during the 2014-15 school year. While CDC reports consistently high vaccination coverage among kindergartners, there are clusters of undervaccinated subgroups that vary demographically. Geospatial analyses can help evaluate local correlations between demographic factors and vaccination coverage, allowing immunization programs to tailor evidence-based interventions to protect communities from vaccine preventable diseases.