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Data and Statistics > Immunization Coverage in the U.S. > NIS
Technical Notes for NIS  Surveillance Tables

Children in the survey period…

were born between
January-December 2002 February 1999 and May 2001
July 2001-June 2002 August 1998 and November 2000
January-December 2001 February 1998 and May 2000
July 2000-June 2001 August 1997 and November 1999
January-December 2000 February 1997 and May 1999
July 1999-June 2000 August 1996 and November 1998
January-December 1999 February 1996 and May 1998
July 1998-June 1999 August 1995 and November 1997
January-December 1998 February 1995 and May 1997
July 1997-June 1998 August 1994 and November 1996
January-December 1997 February 1994 and May 1996
July 1996-June 1997 August 1993 and November 1995

  • The coverage rate among 19 to 35 month-olds reflects immunization practices and programs that were in place for months to more than 2 years before the survey was conducted.  n>Given the length of time required to produce and publish results, these published results reflect immunization practices 2-4 years in the past.
  • 4+DTP refers to 4 or more doses of diphtheria and tetanus toxoids and pertussis vaccine, or diphtheria and tetanus toxoids (DTP/DT/DTaP).
  • 3+polio refers to 3 or more doses of poliovirus vaccine.
  • 1+MCV refers to 1 or more doses of measles-containing vaccine, including MMR.
  • 1+MMR refers to 1 or more doses of a measles-mumps- rubella vaccine.
  • 3+Hib refers to 3 or more doses of Haemophilus influenzae type b (Hib) vaccine.
  • 3+HepB refers to 3 or more doses of hepatitis B vaccine.
  • 1+Var refers to 1 or more doses of varicella vaccine received at or after age 12 months, unadjusted for history of varicella illness.
  • 3+PCV refers to three or more doses of pneumococcal conjugate vaccine.
  • 3:3:1 refers to 3 or more doses of DTP/DT, 3 or more doses of poliovirus vaccine, and 1 or more doses of MCV.
  • 4:3:1 refers to 4 or more doses of DTP/DT, 3 or more doses of poliovirus vaccine, and 1 or more doses of MCV.
  • 4:3:1:3 refers to 4:3:1 and 3 or more doses of Hib.
  • 4:3:1:3:3 refers to 4:3:1:3 and 3 or more doses of Hep B.
  • 4:3:1:3:3:1 refers to 4:3:1:3 and 1 or more doses of varicella.
  • CI refers to a 95% confidence interval. The 95% confidence intervals around the coverage estimates are measures of precision; wide confidence intervals are a sign of a relatively small sample size and relatively less precision. By definition, approximately 5% of the 95% confidence intervals (or about 3 states) will fail to contain the true coverage, that is, the true rate will fall outside of the interval. Exactly how many and which confidence intervals in any given year will fail to contain the true vaccination coverage are unknown and unknowable, but could be as few as 0 or as many as 5.   Consequently, looking at an area’s data over time is also valuable to a correct understanding of apparent changes in coverage. Where confidence intervals overlap, the observed difference might be due to chance.
  • Estimate is listed as NA (Not Available) if the sample size in that subgroup was not sufficiently large to meet the NCHS standard of reliability or precision: if the unweighted sample size for the numerator was <30 or (CI half width)/Estimate <0.5 or (CI half width)>10. In these cases the estimate for that subgroup is not reported, but the individuals are still included in the overall sample and may have an effect on the overall estimate.
  • National rates are based on the entire survey sample of more than 30,000 completed interviews.  Consequently, national vaccination coverage estimates have much smaller (<+ 1%) confidence intervals and are much more precise than state or urban area estimates.
  • Race was self-reported by the respondent.  Hispanic children can be of any race.
  • An area’s vaccination coverage estimate is based on the provider-verified responses from children who live in households with telephones.  Complex statistical methods are used to adjust for children whose parents refuse to participate, those who live in households without telephones, or those whose immunization histories cannot be verified through their providers. 

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This page last modified on July 11, 2003


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