1999 National Health Interview Survey/ National Immunization Provider Record Check Study (NHIS/NIPRCS) Public-Use Data File WARNING - DATA USE RESTRICTIONS! Read Carefully Before Use The Public Health Service Act (Section 308(d)) provides that the data collected by the National Center for Health Statistics (NCHS), Centers for Disease Control and Prevention (CDC), may be used only for the purpose of health statistical reporting and analysis. Any effort to determine the identity of any reported case is prohibited by this law. NCHS does all it can to ensure that the identity of data subjects cannot be disclosed. All direct identifiers, as well as any characteristics that might lead to identification, are omitted from the data files. Any intentional identification or disclosure of a person or establishment violates the assurances of confidentiality given to the providers of the information. Therefore, users will: 1. Use the data in these data files for statistical reporting and analysis only. 2. Make no use of the identity of any person or establishment discovered inadvertently and advise the Director, NCHS, of any such discovery (301-458-4500). 3. Not link these data files with individually identifiable data from other NCHS or non-NCHS data files. By using these data, you signify your agreement to comply with the above-stated statutorily based requirements. Introduction Since 1991, estimates of national vaccination coverage rates for young children have been available through the National Health Interview Survey (NHIS), conducted annually by the National Center for Health Statistics (NCHS) of the Centers for Disesase Control and Prevention (CDC). The NHIS is a national study that collects health-related data from persons living in households selected through a multi-stage area-probability sampling process. The validity of the estimates of vaccination coverage level from the NHIS has been a concern because of the large proportion of respondents who rely on recall to report their child's vaccination history,and questions about the accuracy of reported vaccination histories even when a shot card is used. Therefore, the NCHS and the National Immunization Program (NIP) of the CDC implemented the NHIS/NIPRCS in 1994. The purpose of the NHIS/NIPRCS was to validate the household reports of immunization histories of children between the ages of 12 and 35 months against the records obtained from the immunization providers for these children. General Information The 1999 NHIS/NIPRCS contains data from two sources: the 1999 National Health Interview Survey Immunization Supplement (NHIS/IM) and the Immunization History Questionnaire (IHQ) completed by the medical providers of children for whom immunizations were reported in the NHIS. Variables were also selected from the following NHIS data files: Household, Family, Person, Sample Adult, and Sample Child. In order for households to be eligible for the NHIS/NIPRCS, an NHIS/IM had to have been completed for a child or children aged 12-35 months. As part of completing the NHIS/IM, the parent or legal guardian was asked to sign a form granting permission to contact the child's medical providers. Up to three providers could be named on the permission form. In addition to the parent's or guardian's signature and identifying information, the names and addresses of the immunization providers were captured on the form. Only households that gave permission to contact medical providers could be included in the NHIS/NIPRCS. An IHQ was mailed to the immunization providers to obtain vaccination information for the child. The immunization information provided by household respondents and providers were reconciled for each child. If discrepancies were discovered, then both providers and households could be contacted to resolve the inconsistencies between the reports. To do this, households were asked whether any additional providers should be contacted. Providers were asked to verify the reported vaccination dates, or whether another provider could have the child's immunization records. If discrepancies still remained in the vaccination dates after these contacts with households and providers, the provider information or a combination of the provider information and the household information was determined to be the most accurate or best value for immunization information. Information in this Data Release This public-use data release includes a 1999 NHIS/NIPRCS data file and related documentation. Users of these data must review the descriptive and explanatory documents carefully to analyze the data correctly. The 1999 NHIS/NIPRCS Code Book describes each data variable and its associated response values. The 1999 NHIS/NIPRCS IHQ is included in an appendix in the Data User's Guide. Please refer to the 1999 NHIS documentation for the data collected in the NHIS/IM. It is available from the NCHS website: http://www.cdc.gov/nchs/nhis.htm The 1999 NHIS/NIPRCS Data User's Guide provides specific detail about the design of the 1999 NHIS/NIPRCS, the weighting and estimation procedures, and other important information needed for analyzing the data. Sample Design and Sampling Weights The sample for the NHIS/NIPRCS consists of all children between 12 and 35 months of age for whom the NHIS Immunization Supplement was completed. Therefore, the sample design for the selection of children in the NHIS/NIPRCS is the same as the NHIS/IM. A complete description of the NHIS sample design can be found on the NCHS website: http://www.cdc.gov/nchs/nhis.htm. The NHIS/NIPRCS excludes nonrespondents to the NHIS Immunization Supplement. The sampling weights of children for whom the Immunization Supplement was completed are adjusted to account for this nonresponse. Therefore, the base sampling weight for each child in the NHIS/NIPRCS is the nonresponse-adjusted NHIS Immunization Supplement weight. As mentioned earlier, a best value for the number of shots of each vaccine or series that each child received is determined from a combination of provider and household reports. It is not possible to assign best values to all children in the sample. To compensate for children with missing best values, the sampling weights of children with best values are adjusted, so that they account for all children with or without best values. The weight adjustment is done within weighting classes, which are based on the use of shot cards by household respondents and the household report of the child's up-to-date status on the 4:3:1:3 series. The 1999 NHIS/NIPRCS Data User's Guide includes more detailed discussion of the weighting process. The standard errors of the best value vaccination coverage estimates were computed using the SUDAAN software. However, any commercially available statistical software package capable of analyzing complex survey data (e.g., SAS, STATA) can be used. 1999 NHIS/NIPRCS Data File The NHIS/NIPRCS data file can be merged with the NHIS data files. The files can be merged by using the Household Serial Number (HHX), Family Serial Number (FMX), or Person Number (PX), depending on the file in which the NHIS variable is located. For detailed instruction on merging NHIS variables, please refer to the 1999 NHIS documentation. Contents of the 1999 NHIS/NIPRCS Public-Use File The 1999 NHIS/NIPRCS public-use data file is available in ASCII format. A simple SAS program (in ASCII format) is provided to faciliate reading the ASCII data file and creating a SAS dataset. The SAS program contains, for each variable in the ASCII file, the variable name, its starting and ending positions, labels, and formats. Available files are: File File Name Description Format File Size (KB) NPDUG99.DAT Data File ASCII 2,180 NPCBK99.PDF Code Book PDF 486 NPDUG99.PDF User's Guide PDF 348 NPPUF99.SAS SAS Program ASCII 57 The ASCII file NPPUF99.DAT can be used for processing by any statistical software packages that accept ASCII-formatted input, or it can be transferred to another computer for processing. In order to view PDF documents, the Adobe Acrobat Reader must be installed on your computer. The Adobe Acrobat Reader can be downloaded from the Adobe Acrobat Web site at: http://www.adobe.com/prodindex/acrobat/readstep.html. The 1999 NHIS/NIPRCS files are located at: http://www.cdc.gov/nchs/nhis.htm Guidelines for Citation of Data With the goal of mutual benefit, the National Center for Health Statistics (NCHS) requests that recipients of data files cooperate in certain actions related to their use. Any published material derived from the data should acknowledge NCHS as the original source. The suggested citation to appear at the bottom of all tables is as follows: Source: CDC, NIP and NCHS (2002), 1999 National Health Interview Survey/National Immunization Provider Record Check Study When cited in a bibliography, the citation should read: U.S. Department of Health and Human Services. 1999 National Health Interview Survey/National Immunization Provider Record Check Study (machine readable data file and documentation). National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, MD, 2002. The published material should also include a disclaimer that attributes any analyses, interpretations, or conclusions reached to the author (recipient of the data file) and not to NCHS, which is responsible only for the initial data. Users and analysts who wish to publish a technical description of the data should ensure that the description is not inconsistent with that published by NCHS. Please place the acronym NHIS/NIPRCS in the titles, keywords, or abstracts of journal articles and other publications in order to facilitate the retrieval of such materials in bibliographic searches. Although the data files have been edited carefully, errors may be detected. Please notify NCHS staff of any errors in the 1999 NHIS/NIPRCS data or documentation, and refer to the NCHS website for updates to the NHIS/NIPRCS data files. For additional information on NHIS data products: Phone : 301-458-4901 FAX : 301-458-4035 E-mail : nhislist@cdc.gov Internet: http://www.cdc.gov/nchs/nhis.htm For additional information on other NCHS data products: Phone : 301-458-INFO [301-458-4636] E-mail : nchsquery@cdc.gov Internet: http://www.cdc.gov/nchs