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National, State, and Urban Area Vaccination Coverage Levels Among Children Aged 19-35 Months -- United States, April 1994-March 1995

The National Immunization Survey (NIS) is an ongoing survey to provide national, state, and selected urban area estimates of vaccination coverage levels among children aged 19-35 months. CDC implemented NIS in April 1994 as one element of the five-part Childhood Immunization Initiative (CII) (1), a national strategy to achieve and maintain high vaccination levels among children during the first 2 years of life; CII contains interim goals to the year 2000 national objectives (2). NIS collects quarterly data from all 50 states, the District of Columbia, and 27 urban areas considered to be at high risk for undervaccination. This report provides the results of national, state, and urban area vaccination coverage levels for April 1994-March 1995, which document the highest overall vaccination levels ever achieved for preschool-aged children in the United States, but a wide range (41 percentage points) between areas with the highest and lowest vaccination coverage levels.

NIS uses a two-phase sample design: the first phase employs a quarterly random sample of telephone numbers for each survey area and includes administration of a screening questionnaire to respondents aged greater than or equal to 18 years to locate households with one or more children aged 19-35 months. Vaccination information is collected for age-eligible children. All respondents are asked to refer to written records; however, reports from recall also are accepted. During April 1994-March 1995, approximately 1.6 million telephone numbers were called, and 33,876 interviews were completed (an average of 434 interviews per area). The overall response rate for eligible households was 70% (range: 60%-85% among the 78 survey sites).

In the second phase, vaccination information is requested from health-care providers of children in surveyed households. During 1994, households were excluded that used records indicating their children received all recommended doses of four specific vaccines. * All households identified in the first quarter of 1995 were included in the second phase. Based on exclusions, 27,108 (80%) children were eligible for the second phase; of these, vaccination information was obtained from providers for 11,609 (43%) children. The demographic characteristics and the reported vaccination histories were similar for children in households with and without provider information.

Overall, for 54% of the children in the survey, either written records of having received all of the required doses for the four vaccines were available, or vaccination information based on provider records was available. The data obtained from provider records enabled improvements in the accuracy of the vaccination coverage estimates for the entire sample. Standard two-phase estimation procedures (3) were used to estimate vaccination coverage for each surveyed area. Estimates were adjusted using natality data to create a weighted sample representative of children aged 19-35 months in the United States; in addition, adjustments were made for non-response and for exclusion of households without a telephone because children in households without telephones are less likely to be vaccinated than children in households with a telephone (4; CDC, unpublished data, 1995).

Based on NIS, among children born during May 1991-August 1993 and who were aged 19-35 months (median age: 27 months) at the time of the survey, estimated vaccination coverage was greater than 90% for three or more doses of diphtheria and tetanus toxoids and pertussis vaccine (DTP); coverage for three or more doses of poliovirus vaccine, one dose of measles-mumps- rubella vaccine (MMR), and three or more doses of Haemophilus influenzae type b vaccine (Hib) ranged from 84% to 90% (Table_1). Hepatitis B vaccine coverage was 42% and ranged from 24% for children aged 25-35 months to 58% for children aged 19-24 months.

Estimated vaccination coverage was 75% (95% confidence interval {CI}=plus or minus 1.0%) for receipt of at least four doses of DTP, three doses of poliovirus vaccine, and one dose of MMR (4:3:1 series). When the series was expanded to include three doses of Hib (4:3:1:3 series), estimated coverage levels were 72% (95% CI=plus or minus 1.1%). The lower overall coverage for the 4:3:1 and 4:3:1:3 series compared with coverage for the individual vaccines was accounted for primarily by low coverage for the fourth dose of DTP (77%).

State-specific estimated coverage levels for the 4:3:1 series ranged from 63% (95% CI=plus or minus 5.3%) to 87% (95% CI=plus or minus 4.1%), and for the 4:3:1:3 series from 59% (95% CI=plus or minus 5.3%) to 86% (95% CI=plus or minus 4.2%) (Table_2). Estimated coverage levels among selected large urban areas ranged from 52% (95% CI=plus or minus 8.2%) to 87% (95% CI=plus or minus 5.2%) for the 4:3:1 series, and from 46% (95% CI=plus or minus 8.0%) to 87% (95% CI=plus or minus 5.2%) for the 4:3:1:3 series (Table_3).

To assess the validity of estimates from NIS, findings were compared with coverage estimates from the National Health Interview Survey (NHIS) (CDC, unpublished data, 1995), a national household survey of the U.S. civilian, noninstitutionalized population. During 1994, NHIS data had been supplemented with provider information in the same manner as in NIS. The estimated coverage levels in NIS of 75% for the 4:3:1 series and 72% for the 4:3:1:3 series were similar to those in NHIS (73% and 71%, respectively). Vaccine coverage levels for each vaccine (except for hepatitis B) were nearly identical (Table_1).

Reported by: National Center for Health Statistics; Assessment Br, Data Management Div, National Immunization Program, CDC.

Editorial Note

Editorial Note: The NIS data provide the first population-based state and urban area-specific estimates of vaccination coverage produced by a standard methodology for the United States. NIS permits monitoring of coverage levels of existing vaccines and tracking of the implementation of vaccination with new vaccines. Vaccination coverage estimates from the April 1994-March 1995 NIS and the 1994 NHIS are the highest ever recorded in the United States. In particular, findings from NIS indicate achievement of the 1996 CII goal for 90% coverage with three doses each of DTP and Hib, and the 90% coverage goals for polio and measles were nearly attained (5). Estimated coverage for hepatitis B, the vaccine most recently added to the pediatric schedule, was the lowest because, within the 19-35-month age group, many children were born before this vaccine was recommended (6). Estimated coverage increased with successive age cohorts born after the recommendation for hepatitis B was widely disseminated (Table_1). In addition, the NIS-based estimate of coverage for hepatitis B vaccine probably exceeds that from NHIS because NHIS assessed coverage from January through December 1994, when a higher proportion of children were born before promulgation of the recommendation for universal hepatitis B vaccination. In addition, NIS assessed coverage from April 1994 through March 1995, when all children surveyed were born after the recommendation went into effect.

The Advisory Committee on Immunization Practices recently reaffirmed its recommendation for a fourth dose of DTP for all children aged 12-18 months (1). Recently completed field trials suggest that the efficacy of whole-cell vaccine can decrease substantially greater than 6 months after the third dose and underscore the need for boosting immunity with a fourth dose of DTP (7,8). Findings in this report indicate that coverage with four doses of DTP was the lowest of the four vaccines included in the combined series, emphasizing the importance of intensifying efforts to ensure timely administration of the fourth dose of DTP and the need for simultaneous administration with other vaccines recommended for children aged 12-18 months.

One of the national health objectives for the year 2000 is to achieve series-complete coverage for the recommended vaccines among at least 90% of children aged 2 years (objective 20.11) (2). Series-specific coverage levels that include Hib (i.e., 4:3:1:3 series) are reported here. All children included in the survey were born after October 1990, when recommendations for universal Hib vaccination of infants became effective.

Coverage levels varied substantially by state and large urban areas (e.g., a difference of 27 percentage points in 4:3:1:3 coverage between the states and 41 percentage points between the urban areas with the highest and lowest reported coverage levels). Although reasons for these differences have not been determined, these findings suggest that the national goals are achievable and that effective approaches should be adapted from the most successful areas. Efforts must be intensified to increase coverage among children in those areas with the lowest coverage.

Publication of the state NIS data in August 1995 assisted in strengthening vaccination program activities at the state level in some areas with the lowest coverage (9). For example, in Michigan, related efforts have included creation of a new plan to address undervaccination; organization of meetings with health-care providers, community groups, and business leaders to discuss undervaccination; and conducting an immunization summit at which the Michigan Department of Public Health initiated a new statewide vaccination information campaign. In Missouri, the governor established as a priority the need to increase vaccination levels of children aged less than 2 years and established goals of increasing levels to 75% by 1996 and to 90% by 1997. CDC will continue to use data from NIS and NHIS to evaluate progress toward national vaccination goals and to stimulate further efforts to improve vaccination coverage.

References

  1. CDC. Reported vaccine-preventable diseases -- United States, 1993, and the Childhood Immunization Initiative. MMWR 1994;43:57-60.

  2. Public Health Service. Healthy people 2000: national health promotion and disease prevention objectives -- full report, with commentary. Washington, DC: US Department of Health and Human Services, Public Health Service, 1991; DHHS publication no. (PHS)91-50212.

  3. Cochran WG. Double sampling. In: Cochran WG. Sampling techniques. 3rd ed. New York: John Wiley & Sons, Inc, 1977:327-58.

  4. Massey JT, Botman SL. Weighting adjustments for random digit dialed surveys. In: Groves RM, Biemer PP, Lyberg LE, Massey JT, Nicholls WL, Waksborg J. Telephone survey methodology. New York: John Wiley & Sons, Inc, 1988:143-60.

  5. CDC. Recommended childhood immunization schedule -- United States, 1995. MMWR 1995; 44(no. RR-5).

  6. CDC. Hepatitis B virus: a comprehensive strategy for eliminating transmission in the United States through universal childhood vaccination: recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR 1991;40(no. RR-13).

  7. Greco D, Salmaso S, Mastrantonio P, et al. A controlled trial of two acellular vaccines and one whole-cell vaccine against pertussis. N Engl J Med 1996;334:341-8.

  8. Gustafsson L, Hallander HO, Olin P, Reizenstein E, Storsaeter J. A controlled trial of a two-compound acellular, a five-component acellular, and a whole-cell pertussis vaccine. N Engl J Med 1996;334: 349-55.

  9. CDC. State and national vaccination coverage levels among children aged 19-35 months -- United States, April-December 1994. MMWR 1995;44: 613,619-23.

These vaccines were four doses of diphtheria and tetanus toxoids and pertussis vaccine, three doses of poliovirus vaccine, one dose of measles- mumps-rubella vaccine, and three doses of Haemophilus influenzae type b vaccine.

+------------------------------------------------------------------- ------+ |             | | Erratum: Vol. 45, No. 7 | |             | | SOURCE: MMWR 45(09);196 DATE: Mar 08, 1996 | |             | | In the report, "National, State, and Urban Area Vaccination | | Coverage Levels Among Children Aged 19-35 Months -- United States, | | April 1994-March 1995," on page 149 in Table_3 in the column for | | 4:3:1:3 series coverage, the percentage coverage for Chicago should | | be 55.      | |             | +------------------------------------------------------------------- ------+
Table_1
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TABLE 1. Vaccination coverage levels among children aged 19-35 months, by selected
vaccines -- National Immunization Survey (NIS), United States, April 1994-March 1995
--------------------------------------------------------------------------------------
                                                    NHIS *          NIS+
                           1996   Year 2000   ----------------  ----------------------
Vaccine/Dose               Goal   Objective    %   (95% CI+)    %  (95% CI)
--------------------------------------------------------------------------------------
DTP/DT &
  >=3 Doses                 90%       90%      93   (+/- 1.4%)  94 (+/-0.6%)
  >=4 Doses                 --        90%      75   (+/- 2.4%)  77 (+/-1.0%)
Poliovirus
  >=3 Doses                 90%       90%      83   (+/- 2.2%)  84 (+/-0.9%)
Haemophilus influenzae
  type B
  >=3 Doses                 90%       90%      89   (+/- 1.8%)  90 (+/-0.7%)
MMR @
 >=1 Dose                   90%       90%      87   (+/- 1.8%)  89 (+/-0.8%)
Hepatitis B
 >=3 Doses                  70%       90%      26   (+/- 2.2%)  42 (+/-1.2%)
   19-24 months                                41   (+ 4.1%)    58 (+/-1.4%)
   25-30 months                                23   (+ 3.5%)    41 (+/-1.4%)
   31-35 months                                10   (+ 2.9%)    24 (+/-1.3%)
Combined series
  4 DTP/3 Polio/1 MMR **    --        90%      73   (+/- 2.4%)  75 (+/-1.0%)
  4 DTP/3 Polio/1 MMR/
    3 Hib ++                --        90%      71   (+/- 2.4%)  72 (+/-1.1%)
--------------------------------------------------------------------------------------
*  1994 National Health Interview Survey.
+  Confidence interval.
&  Diphtheria and tetanus toxoids and pertussis vaccine/Diphtheria and tetanus
   toxoids.
@  Measles-mumps-rubella vaccine.
** Four doses of DTP/DT, three doses of poliovirus vaccine, and one dose of MMR.
++ Four doses of DTP/DT, three doses of poliovirus vaccine, one dose of MMR, and three
   doses of Hib.
======================================================================================


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Table_2
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TABLE 2. Estimated vaccination coverage with the 4:3:1 series * and 4:3:1:3 series +, by coverage
level and state -- National Immunization Survey, United States, April 1995-March 1995
====================================================================================================
                      4:3:1 Series coverage                           4:3:1:3 Series coverage
Coverage level/      -----------------------  Coverage level/      ---------------------------------
 State                 %        (95% CI &)     State                  %             (95% CI)
----------------------------------------------------------------------------------------------------
>=85%                                          >=85%
 Connecticut           86        (+/-4.8%)       Vermont              86            (+/-4.2%)
 Massachusetts         85        (+/-4.2%)      75%-84%
 Vermont               87        (+/-4.1%)       Connecticut          84            (+/-5.2%)
75%-84%                                          Delaware             79            (+/-5.8%)
 Arizona               77        (+/-4.3%)       Florida              78            (+/-4.9%)
 Colorado              76        (+/-5.8%)       Georgia              75            (+/-5.4%)
 Delaware              81        (+/-5.7%)       Hawaii               80            (+/-5.6%)
 Florida               79        (+/-4.8%)       Iowa                 82            (+/-4.8%)
 Georgia               76        (+/-5.3%)       Kansas               79            (+/-5.1%)
 Hawaii                84        (+/-5.1%)       Kentucky             80            (+/-5.3%)
 Iowa                  83        (+/-4.5%)       Maine                80            (+/-5.1%)
 Kansas                82        (+/-4.8%)       Maryland             77            (+/-4.8%)
 Kentucky              81        (+/-5.2%)       Massachusetts        83            (+/-4.5%)
 Maine                 83        (+/-4.9%)       Minnesota            77            (+/-5.3%)
 Maryland              79        (+/-4.6%)       Mississippi          80            (+/-5.5%)
 Minnesota             78        (+/-5.2%)       New Hampshire        82            (+/-5.2%)
 Mississippi           80        (+/-5.5%)       New York             75            (+/-4.6%)
 New Hampshire         84        (+/-5.0%)       North Carolina       79            (+/-5.6%)
 New York              76        (+/-4.5%)       North Dakota         80            (+/-4.5%)
 North Carolina        83        (+/-5.3%)       Pennsylvania         76            (+/-4.6%)
 North Dakota          82        (+/-4.4%)       Rhode Island         81            (+/-5.2%)
 Pennsylvania          78        (+/-4.4%)       South Carolina       79            (+/-5.3%)
 Rhode Island          83        (+/-5.0%)       Virginia             77            (+/-5.8%)
 South Carolina        81        (+/-5.3%)       Wyoming              76            (+/-5.4%)
 South Dakota          76        (+/-5.6%)      65%-74%
 Virginia              78        (+/-5.8%)       Alabama              73            (+/-5.3%)
 Washington            75        (+/-4.2%)       Alaska               68            (+/-6.2%)
 Wisconsin             76        (+/-4.4%)       Arizona              74            (+/-4.5%)
 Wyoming               79        (+/-5.2%)       Arkansas             66            (+/-6.1%)
65%-74%                                          California           70            (+/-4.6%)
 Alabama               74        (+/-5.2%)       Colorado             73            (+/-6.1%)
 Alaska                72        (+/-6.1%)       Idaho                65            (+/-6.3%)
 Arkansas              69        (+/-6.0%)       Indiana              70            (+/-5.1%)
 California            73        (+/-4.5%)       Louisiana            72            (+/-5.4%)
 Idaho                 66        (+/-6.3%)       Missouri             66            (+/-6.5%)
 Illinois              69        (+/-5.1%)       Montana              71            (+/-5.7%)
 Indiana               72        (+/-5.0%)       Nebraska             67            (+/-5.9%)
 Louisiana             74        (+/-5.3%)       Nevada               65            (+/-6.6%)
 Missouri              67        (+/-6.5%)       New Jersey           69            (+/-6.0%)
 Montana               72        (+/-5.7%)       New Mexico           70            (+/-6.5%)
 Nebraska              72        (+/-5.7%)       Ohio                 73            (+/-4.6%)
 Nevada                68        (+/-6.5%)       Oklahoma             70            (+/-6.7%)
 New Jersey            70        (+/-5.9%)       Oregon               65            (+/-6.3%)
 New Mexico            73        (+/-6.2%)       South Dakota         74            (+/-5.7%)
 Ohio                  74        (+/-4.6%)       Tennessee            70            (+/-4.3%)
 Oklahoma              73        (+/-6.6%)       Texas                68            (+/-3.9%)
 Oregon                67        (+/-6.2%)       Utah                 67            (+/-4.9%)
 Tennessee             73        (+/-4.2%)       Washington           73            (+/-4.3%)
 Texas                 71        (+/-3.8%)       West Virginia        68            (+/-6.3%)
 Utah                  70        (+/-4.8%)       Wisconsin            74            (+/-4.4%)
 West Virginia         69        (+/-6.3%)      <65%
<65%                                             Illinois             64            (+/-5.2%)
 Michigan              63        (+/-5.3%)       Michigan             59            (+/-5.3%)

Total                 75         (+/-1.0%)      Total                 72            (+/-1.1%)
----------------------------------------------------------------------------------------------------
* Four doses of diphtheria and tetanus toxoids and pertussis vaccine/Diphtheria and tetanus toxoids
  (DTP/DT), three doses of poliovirus vaccine, and one dose of measles-mumps-rubella vaccine (MMR).
+ Four doses of DTP/DT, three doses of poliovirus vaccine, one dose of MMR, and three doses of
  Haemophilus influenzae type B vaccine.
& Confidence interval.
====================================================================================================

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Table_3
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TABLE 3. Estimated vaccination coverage with the 4:3:1 series * and the 4:3:1:3 series + for selected
metropolitan areas -- National Immunization Survey, United States, April 1994-March 1995
=======================================================================================================
                         4:3:1 Series coverage                           4:3:1:3 Series coverage
Coverage level/         ------------------------ Coverage level/      ---------------------------------
 Area                     %           (95% CI&)   Area                       %        (95% CI)
-------------------------------------------------------------------------------------------------------
>=85%                                             >=85%
 Boston                  87           (+/- 5.2%)    Boston                   87      (+/- 5.2%)
 Santa Clara Co., Calif. 85           (+/- 4.9%)   75%-84%
75%-84%                                             Baltimore                77      (+/- 6.1%)
 Baltimore               80           (+/- 5.8%)    Cuyahoga Co., Ohio       82      (+/- 5.5%)
 Cuyahoga Co., Ohio      84           (+/- 5.3%)    El Paso Co., Tex.        79      (+/- 5.4%)
 Dade Co., Fla.          77           (+/- 6.4%)    Fulton/DeKalb cos., Ga.  75      (+/- 6.9%)
 El Paso Co., Tex.       82           (+/- 5.1%)    Jefferson Co., Ala.      75      (+/- 6.3%)
 Fulton/DeKalb cos., Ga. 77           (+/- 6.7%)    Marion Co., Ind.         78      (+/- 6.1%)
 Jefferson Co., Ala.     78           (+/- 6.0%)    Milwaukee Co., Wis.      77      (+/- 6.0%)
 Kings Co., Wash.        78           (+/- 5.3%)    New York City            75      (+/- 6.5%)
 Maricopa Co., Ariz.     77           (+/- 6.1%)    Santa Clara Co., Calif.  80      (+/- 5.6%)
 Marion Co., Ind.        81           (+/- 5.8%)   65%-74%
 Milwaukee Co., Wis.     80           (+/- 5.7%)    Dade Co., Fla.           74      (+/- 6.6%)
 New York City           76           (+/- 6.5%)    Dallas Co., Tex.         66      (+/- 7.0%)
65%-74%                                             Davidson Co., Tenn.      67      (+/- 6.4%)
 Bexar Co., Tex.         67           (+/- 6.5%)    District of Columbia     67      (+/- 7.3%)
 Dallas Co., Tex.        71           (+/- 6.6%)    Duval Co., Fla.          71      (+/- 6.2%)
 Davidson Co., Tenn.     69           (+/- 6.3%)    Franklin Co., Ohio       70      (+/- 6.8%)
 District of Columbia    72           (+/- 7.0%)    Kings Co., Wash.         74      (+/- 5.6%)
 Duval Co., Fla.         74           (+/- 6.0%)    Los Angeles Co., Calif.  68      (+/- 7.7%)
 Franklin Co., Ohio      71           (+/- 6.8%)    Maricopa Co., Ariz.      74      (+/- 6.3%)
 Los Angeles Co., Calif. 73           (+/- 7.5%)    Orleans Parish, La.      66      (+/- 7.8%)
 Orleans Parish, La.     67           (+/- 7.8%)    Philadelphia Co., Pa.    69      (+/- 7.4%)
 Philadelphia Co., Pa.   71           (+/- 7.3%)    San Diego, Co., Calif.   72      (+/- 5.8%)
 San Diego Co., Calif.   74           (+/- 5.8%)    Shelby Co., Tenn.        71      (+/- 7.0%)
 Shelby Co., Tenn.       73           (+/- 6.9%)   <65%
<65%                                                Bexar Co., Tex.          64      (+/- 6.6%)
 Chicago                 61           (+/- 8.7%)    Chicago                  61      (+/- 8.7%)
 Detroit                 52           (+/- 8.2%)    Detroit                  46      (+/- 8.0%)
 Houston                 62           (+/- 8.1%)    Houston                  58      (+/- 8.0%)
 Newark, N.J.            62           (+/-10.0%)    Newark, N.J.             55      (+/-10.1%)
-------------------------------------------------------------------------------------------------------
* Four doses of diphtheria and tetanus toxoids and pertussis vaccine/Diphtheria and tetanus toxoids
  (DTP/DT), three doses of poliovirus vaccine, and one dose of measles-mumps-rubella vaccine (MMR).
+ Four doses of DTP, three doses of poliovirus vaccine, one dose of MMR, and three doses of
  Haemophilus influenzae type B vaccine.
& Confidence interval.
=======================================================================================================

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