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NIS Data Analysis Methodologies

The statistical methodology for estimating vaccination coverage rates for NIS data was changed in 1998. The new methodology facilitates valid statistical analyses of NIS data that appropriately accounts for the survey's complex sampling design. Small differences exist between vaccination coverage estimates appearing in MMWRs published before 1998 and estimates published on this website.

The pre 1998 methodology is described in Zell, E.R., Ezzati-Rice, T.M., Battaglia, M.P., and Wright, R.A. (2000). National Immunization Survey: The methodology of a vaccination surveillance system. Public Health Reports, 115(1), 65-77.

The new methodology is described in Smith, P.J., Rao, J.N.K., Battaglia, M.P., Ezzati-Rice, T.M., Daniels, D., Khare, M. (2001). Compensating for provider nonresponse using response propensities to form adjustment cells: the National Immunization Survey. National Center for Health Statistics. Vital Statistics 2(133).

All estimates published on this website are calculated using this new methodology.