Unvaccinated Children in the United States: Trends and Characteristics. Analysis of the National Immunization Survey (NIS), 2002-2006

Laura Blakeslee, University of Wisconsin at Madison

Previous analyses of vaccine status have focused mostly on characteristics of fully-vaccinated versus under-vaccinated children (not distinguishing between children who are un-vaccinated and partly-vaccinated). However, studies indicate recent outbreaks of infectious disease in the United States are due partly to un-vaccinated children whose parents forgo immunizations because of vaccine safety concerns or low perceived risk of disease. Using the National Immunization Survey (NIS, 2002-2006), I find a significant increase over five years in the proportion of U.S. children 19-36 months who remain un-vaccinated. Also, vaccine status varies significantly by child, mother and household characteristics (race/ethnicity, WIC, breastfeeding, mother’s education, income, family size, region). Whereas prior studies find more lower SES children are under-vaccinated (presumably due to economic constraints), I find higher SES children are more likely to be un-vaccinated altogether (possibly reflecting parental beliefs and choices). Understanding these characteristics is one step towards reducing the incidence of preventable disease.