National Immunization Survey: The methodology of a vaccination surveillance system

The National Immunization Survey (NIS) was designed to measure vaccination coverage estimates for the US, the 50 states, and selected urban areas for children ages 19-35 months. The NIS includes a random-digit-dialed telephon e survey and a provider record check study. Data are weighted to account fo r the sample design and to reduce nonresponse and non-coverage biases in or der to improve vaccination coverage estimates. Adjustments are made for bia ses resulting from nonresponse and nontelephone households and estimation p rocedures are used to reduce measurement bias, The NIS coverage estimates represent all US children, not just children liv ing in households with telephones. NIS estimates are highly comparable to v accination estimates derived from the National Health Interview Survey. The NIS allows comparisons between states and urban areas over time and is used to evaluate current and new vaccination strategies.