Vaccination Coverage of 2-Year-Old Children -- United States, January-March, 1994

The Childhood Immunization Initiative (CII) * was initiated to increase vaccination coverage among 2-year-old children. The 1996 objective is to have at least 90% coverage for four of the five critical vaccines routinely recommended for children (i.e., one dose of measles-mumps-rubella vaccine {MMR} and at least three doses each of diphtheria and tetanus toxoids and pertussis vaccine {DTP}, oral poliovirus vaccine, and Haemophilus influenzae type b vaccine {Hib}), and at least 70% coverage for three doses of hepatitis B vaccine (Hep B) (1). These objectives are an interim step toward the year 2000 goal of at least 90% coverage for the recommended series of vaccinations and are being monitored on an ongoing basis. This report presents national estimates of vaccination coverage among 2-year-old children derived from provisional data from the National Health Interview Survey (NHIS) for the first quarter of 1994 and compares these with the last two quarters of 1993.

The NHIS, a probability sample of the civilian, noninstitutionalized U.S. population, provides quarterly data that enables calculation of national coverage estimates (2). Quarterly estimates for children aged 19-35 months were based on sample sizes of 483 (third quarter 1993), 490 (fourth quarter 1993), and 608 (first quarter 1994). Children included in the survey during the first quarter of 1994 were born during February 1991-August 1992; their median age was 27 months. For the last two quarters in 1993, 37% of NHIS respondents used a vaccination record for reporting vaccination information; for the first quarter of 1994, the use of vaccination records increased to 52%. For the other respondents, such records were unavailable, and information was based on parental recall. Overall, 12%-16% of respondents were excluded because they either reported not knowing whether a child had received a particular vaccination or did not know the number of doses the child had received. Confidence intervals were calculated using SUDAAN.

During the first quarter of 1994, vaccination coverage levels for children aged 19-35 months ranged from 89.6% for measles-containing vaccine (MCV) to 25.5% for Hep B vaccine Table_1. Coverage for the most critical doses for the 1996 objective ranged from 70.6% ( greater than or equal to 3 doses Hib) to 89.6% (MCV). Coverage for the year 2000 goal for the combined series of four doses of DTP, three doses of polio vaccine, and one dose of MCV was 66.0%.

During the last two quarters of 1993 and the first quarter of 1994, vaccination levels have remained statistically unchanged for the combined series and individual antigens with the exception of Hib and Hep B. For the first quarter of 1994, coverage with three doses of Hib vaccine increased significantly from the third quarter of 1993 to a record high of 70.6%, and Hep B coverage increased from 15.7% in the third quarter of 1993 to 25.5% during the first quarter of 1994. Reported by: Assessment Br, Div of Data Management, National Immunization Program, CDC.

Editorial Note

Editorial Note: The findings in this report document recent statistically significant increases in the national vaccination levels for Hib and Hep B. In addition, vaccination levels are near the highest ever recorded for three doses of DTP, three doses of polio vaccine, and one dose of MCV and for the combined series. Despite these improved levels of coverage, however, the findings in this report indicate that coverage levels are 3-19 percentage points below the interim objectives for DTP, polio, and Hib. Coverage levels for Hep B vaccine are the furthest from the 1996 goal. However, because recommendations for universal Hep B vaccination of infants became effective in November 1991, only approximately half of the children in the survey were eligible for Hep B vaccine. An estimated 2 million children aged 19-35 months still need one or more doses of DTP, polio, or MMR vaccine to be completely vaccinated with the combined series of four doses of DTP, three doses of polio vaccine, and one dose of MCV.

The levels for three doses of DTP, three doses of polio vaccine, one dose of MCV, and for the combined series have been constant for three quarters, suggesting that coverage levels may have plateaued. However, such data should be interpreted with caution; the larger number of children in the annual samples provides greater precision for those estimates than the quarterly samples.

To achieve the interim objective for 1996, efforts to implement CII must be accelerated. In particular, as emphasized by the Standards for Pediatric Immunization Practices (3), providers should use all opportunities to vaccinate children, regardless of the reason for the visit (e.g., sick- or well-child visit) -- taking advantage of missed opportunities potentially may increase coverage by 8-22 percentage points (4,5). Because health-care providers may believe coverage levels within their practices are higher than actual levels (6), CDC recommends that providers conduct coverage level assessments; information obtained from such assessments will assist providers in recognizing undervaccination in their practices and in instituting measures to increase coverage. In addition, providers should inform parents about the specific number of vaccine doses needed before age two years (11-15 doses), and parents should be encouraged to review their child's vaccination status at each visit to a health-care provider.

References

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

2. Massey JT, Moore TF, Parsons VL, et al. Design and estimation for the National Health Interview Survey, 1985-94. Hyattsville, Maryland: US Department of Health and Human Services, Public Health Service, CDC, 1989. (Vital and health statistics; series 2, no.

4. Ad Hoc Working Group for the Development of Standards for Immunization Practices. Standards for immunization practice. JAMA 1993;269:1817-22.

5. Dietz VJ, Stevenson J, Zell ER, Cochi S, Hadler S, Eddins D. Potential impact on vaccination coverage levels by administering vaccines simultaneously and reducing dropout rates. Archives of Pediatrics and Adolescent Medicine 1994;148:943-9.

6. CDC. Impact of missed opportunities to vaccinate preschool-aged children on vaccination coverage levels -- selected U.S. sites, 1991- 1992. MMWR 1994;43:709-11,717-8.

7. Bushnell C, Link DA. Private provider assessment. In: 28th National Immunization Conference proceedings. Atlanta: US Department of Health and Human Services, Public Health Service, CDC. (in press).

* The purposes of CII are to 1) improve delivery of vaccines to children; 2) reduce the cost of vaccines for parents; 3) enhance awareness, partnerships, and community participation to improve vaccination coverage; 4) monitor vaccination coverage and occurrence of disease; and 5) improve vaccines and their use.

TABLE 1. Vaccination levels among children aged 19-35 months, by selected vaccines -- United States,
third and fourth quarters 1993 and first quarter 1994
====================================================================================================
                             Third quarter 1993       Fourth quarter 1993      First quarter 1994
                            ---------------------    --------------------    ---------------------
Vaccine                     %        (95% CI *)        %       (95% CI)         %       (95% CI)
----------------------------------------------------------------------------------------------------
DTP/DT +
  >=3 Doses                 89.9    (86.9%-93.9%)    88.1  (84.6%-91.6%)     87.0  (83.2%-90.8%)
  >=4 Doses                 74.8    (69.9%-79.7%)    71.6  (66.4%-76.7%)     67.2  (62.8%-71.7%)

Poliovirus
  >=3 Doses                 80.4    (75.8%-84.9%)    78.5  (73.9%-83.0%)     76.0  (71.9%-80.2%)

Haemophilus influenzae
  type b &
  >=3 Doses                 60.3    (55.0%-65.7%)    58.3  (53.1%-63.5%)     70.6  (65.9%-75.3%)

Measles-containing
  vaccine (MCV)             85.9    (82.0%-89.8%)    86.9  (83.3%-90.5%)     89.6  (87.0%-92.2%)

Hepatitis B @
  >=3 Doses                 15.7    (12.1%-19.2%)    22.5  (17.8%-27.1%)     25.5  (20.2%-30.8%)

3 DTP/3 Polio/1 MCV **      78.7    (74.2%-83.2%)    74.3  (69.4%-79.2%)     75.5  (71.1%-80.0%)

4 DTP/3 Polio/1 MCV ++      71.6    (66.7%-76.4%)    66.4  (61.1%-71.7%)     66.0  (61.4%-70.6%)
----------------------------------------------------------------------------------------------------
 * Confidence interval.
 + Diphtheria and tetanus toxoids and pertussis vaccine/Diphtheria and tetanus toxoids.
 & January-March 1994 was the first time all surveyed children were born after the recommendation for the series.
 @ Children born after the recommendation for universal vaccination varied by quarter: 12% for third quarter 1993, 29%
   for fourth quarter 1993, and 47% for first quarter 1994.
** Three doses of DTP/DT, three doses of poliovirus, and one dose of MCV.
++ Four doses of DTP/DT, three doses of poliovirus, and one dose of MCV.
====================================================================================================

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