Frequently Asked Questions (FAQs)

Questions and answers about child vaccination coverage in the United States

1. What is the purpose of the NIS?
The National Immunization Survey, or NIS, was established to provide on-going, consistent data for analyzing vaccination levels among young children in the United States. The NIS provides national, regional, state, and selected local area estimates of vaccination coverage for vaccines recommended by the Advisory Committee on Immunization Practices (ACIP). It also helps CDC and immunization partners track progress towards Healthy People 2020 goals.

2. Why measure vaccination coverage?
Data on childhood vaccination coverage are used to:

• Identify groups of children at risk of vaccine-preventable diseases like measles and whooping cough (pertussis),
• Provide vaccination coverage estimates in an effort to increase coverage,
• Determine what additional efforts are needed to increase coverage, and
• Evaluate the effectiveness of programs designed to increase coverage to protect children.

3. How are data for the NIS collected?
The NIS uses a nationally-representative sample to estimate vaccination coverage weighted to represent the entire population for the nation, each HHS region, each state, and selected local areas. We use random-digit-dialing to find households with children 19 to 35 months. We ask parents or guardians to share information about their household and child with us. At the end of the interview, we ask for permission to contact the child's vaccination providers. Providers are then contacted by mail to provide each child's vaccination history. The providers send the children’s vaccination history to NIS.

4. What are the strengths of NIS?
The NIS uses a nationally representative sample to estimate vaccination coverage weighted to represent the entire population for the nation, each HHS region, state, and selected local areas. The large sample size allows us to estimate vaccination coverage among different groups, for instance, by income level, race/ethnicity, education level of mothers, and other factors. Vaccination coverage estimates are based on vaccination provider report and not parental recall. 

5. My area's coverage level is lower than last year, but our vaccination program is strong and we did not expect a drop. How should we interpret this information?
The NIS uses a large sample of children to estimate vaccination coverage, about 15,000 children with adequate provider data. It does not include all children 19 to 35 months. Sample estimates and population values may be different due to random variations. The NIS estimates include a margin of error to estimate this difference through a 95% confidence interval. For example, in 2014, the vaccination coverage estimate for 1 dose of measles, mumps, and rubella vaccine in United States was 91.5% +/- 0.9%. This means that the true coverage was probably between 90.6% and 92.4%.

6. What are the vaccination coverage estimates for my local area?
The NIS estimates vaccination coverage for the 50 states and selected local areas and territories. Data are available on ChildVaxView Interactive!