How to Use the NIS-Teen Vaccination Coverage Data

The National Immunization Survey-Teen (NIS-Teen) has a sample size of about 20,000 parents and caregivers answering the household questionnaire. However, the sample is not the entire population, and thus sample estimates and population values are likely to be different. The magnitude of the likely difference is quantified through the 95% confidence interval (CI). For example, in 2008, the vaccination coverage estimate for 1 dose of meningococcal vaccine in Alabama was 29.9% (CI=24.8-35.5). This means that the true coverage was probably between 24.8% and 35.5%. When comparing two estimates (e.g., between states or between years), an overlap in the confidence intervals indicates that the observed difference might be due to chance.