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National, State, and Urban Area Vaccination Coverage Among Children Aged 19--35 Months --- United States, 2004
The National Immunization Survey (NIS) provides vaccination coverage estimates for children aged 19--35 months for each of the 50 states and 28 selected urban areas.* This report summarizes results from the 2004 NIS, which indicated nationwide increases in coverage with at least 1 dose of varicella vaccine (VAR), pneumococcal conjugate vaccine (PCV), and the 4:3:1,§ 4:3:1:3:3,¶ and 4:3:1:3:3:1** vaccine series. These levels represent an important accomplishment by exceeding for the first time the Healthy People 2010 goal of >80% coverage for the 4:3:1:3:3 vaccine series.
To collect vaccination data for age-eligible children, NIS uses a quarterly random-digit--dialing sample of telephone numbers for each of the 78 survey areas. NIS methodology, including the weighting of responses to represent the entire population of children aged 19--35 months, has been described previously (1). During 2004, health-care provider vaccination records were obtained for 21,998 children. The overall survey response rate for eligible households was 67.4%.
National coverage estimates increased from 2003 to 2004 for two of the more recently implemented vaccines, VAR and PCV (Table 1). Coverage estimates for all other vaccines were not substantially different from 2003 to 2004. For the combined vaccine series 4:3:1, 4:3:1:3:3, and 4:3:1:3:3:1, national coverage increased from 2003 to 2004 (Table 1).
However, as in previous years, estimated vaccination coverage levels still varied substantially among states (Table 2). Estimated coverage with the 4:3:1:3:3 series ranged from 89.1% in Massachusetts to 68.4% in Nevada. Coverage also ranged substantially among the 28 urban areas. The highest estimated coverage among the urban areas for the 4:3:1:3:3 series was 89.7% for Davidson County, Tennessee, and the lowest was 64.8% for El Paso County, Texas.
Reported by: N Darling, MPH, T Santibanez, PhD, J Santoli, MD, Immunization Svcs Div, National Immunization Program, CDC.
The findings in this report indicate that, for the first time, vaccination coverage (80.9%) for the 4:3:1:3:3 series exceeded the Healthy People 2010 goal (objective 14-24a) (2) to increase to at least 80% the proportion of children aged 19--35 months who receive all vaccines recommended for universal administration for at least 5 years. Beginning with next year's report on the 2005 NIS, the series measure 4:3:1:3:3:1 (76.0% in 2004) will be used to evaluate progress toward the Healthy People 2010 goal because, beginning with the survey cohort, varicella vaccination will have been recommended for universal administration for 5 years.
The vaccination coverage levels described in this report are notable given shortages in the supplies of several vaccines during 2001--2004. For example, DTaP shortages persisted for more than 1 year, beginning in March 2001 and resolving by July 2002. Shortages for PCV also began in mid-year 2001 and ended in May 2003, only to become short again in early 2004; the PCV shortage ended in September 2004 (3--5). Because vaccine supply shortages are likely to reoccur (6,7), as evidenced by the shortages of influenza vaccine during both the 2003--04 and 2004--05 influenza seasons (8,9), strategies to manage vaccine supply and continued monitoring of the effects of shortages on coverage are needed.
The findings in this report are subject to at least three limitations. First, NIS is a telephone survey; although NIS results are weighted to make them representative of all children aged 19--35 months, these statistical adjustments might not fully represent all the complexities of the survey (e.g., accounting for nonresponse and households without telephones). Second, NIS uses provider-verified vaccination histories and assumes that coverage among children whose providers did not respond is similar to that among children whose providers did respond; thus, incomplete reporting might have resulted in underestimates of coverage. Third, although national estimates are precise (10), estimates for states and urban areas should be interpreted with caution because of wider confidence intervals.
NIS is routinely used to monitor vaccination status among preschool-aged children; however, NIS could be expanded for measuring vaccination coverage among other age groups and for newer vaccines as they become licensed and recommended. In a 2004 pilot study, NIS was used to estimate vaccination coverage among adolescents; analysis of these data is ongoing. In 2003 and 2004, another expansion of NIS, the National Adult Immunization Survey (NAIS), was used to assess influenza and pneumococcal polysaccharide vaccination coverage and reasons for nonvaccination among adults aged >50 years. In 2004, NIS began measuring influenza vaccination coverage among children aged 6--23 months. Several vaccines are newly recommended for various age groups (e.g., meningococcal conjugate [MCV4] and tetanus, diphtheria, and acellular pertussis [Tdap] vaccines) with several others likely to be licensed in the near future (e.g., measles-mumps-rubella-varicella [MMRV], rotavirus, human papillomavirus [HPV], and zoster vaccines). These developments underscore the importance of survey systems such as NIS in monitoring new vaccine implementation, which in turn can provide valuable information for enhancing vaccine uptake.
* Jefferson County, Alabama; Maricopa County, Arizona; Los Angeles, San Diego, and Santa Clara counties, California; District of Columbia; Miami-Dade and Duval counties, Florida; Fulton/Dekalb counties, Georgia; Chicago, Illinois; Marion County, Indiana; Orleans Parish, Louisiana; Baltimore, Maryland; Boston, Massachusetts; Detroit, Michigan; Newark, New Jersey; New York, New York; Cuyahoga and Franklin counties, Ohio; Philadelphia County, Pennsylvania; Davidson and Shelby counties, Tennessee; Bexar, Dallas, and El Paso counties, and Houston, Texas; King County, Washington; and Milwaukee County, Wisconsin.
During the 2004 reporting period, NIS included children born during February 2001--June 2003.
§ >4 doses of diphtheria, tetanus toxoids and pertussis vaccines, diphtheria and tetanus toxoids, and diphtheria, tetanus toxoids and any acellular pertussis vaccine (DTP/DT/DTaP); >3 doses of poliovirus vaccine; and >1 dose of any measles-containing vaccine.
¶ 4:3:1 plus >3 doses of Haemophilus influenzae type b (Hib) vaccine and >3 doses of hepatitis B vaccine.
** 4:3:1:3:3 plus >1 dose of VAR.
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Date last reviewed: 7/27/2005