August 1996
ATLANTA — An ongoing survey developed by the Centers for Disease Control and Prevention (CDC) has revealed that most vaccination coverage levels among children 19 months to 35 months old have steadily increased.
Results from the National Immunization Survey (NIS) conducted from July 1994 to June 1995 reveal that national coverage levels for Haemophilus influenzae type b vaccine (Hib), poliovirus vaccine, diphtheria and tetanus toxoids and pertussis vaccine (DTP) and hepatitis B vaccine (hepB) have met or exceeded the 1995 interim goals of the Childhood Immunization Initiative (CII). The CII is a five-part national strategy to achieve and maintain high immunization levels among children 2 years of age and younger.
Coverage for measles-mumps-rubella (MMR) vaccine fell within one percentage point of the CII objective.
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First implemented in April 1994, the NIS uses a two-phase sample design to collect quarterly data from all 50 states, the District of Columbia and urban areas thought to be at increased risk for under-vaccination.
The first phase uses a quarterly random sample of telephone numbers for every survey area. A screening questionnaire geared to respondents ages 18 years and older locates households with one or more children ages 19 months to 35 months. Respondents provide vaccination information for all age-eligible children from written records or from personal recall.
In the second phase, health-care providers supply vaccination information for children in the surveyed households.
Between July 1994 and June 1995, the first phase of the study yielded approximately 35,440 completed household interviews; the overall response rate for eligible households was 71%.
In 1994, households that indicated their children received all recommended doses of four specific vaccines (four doses of DTP, three doses of poliovirus vaccine, one dose of MMR, and three doses of Hib) were excluded from the survey. Based on these exclusions, 30,543 children (86%) were eligible for the second phase of the survey. Of these, health care providers submitted vaccination information for 13,755 children (45%). Vaccination histories and demographic characteristics were similar for children regardless of whether or not providers supplied vaccination records.
Overall, for 59% of children in the survey, roughly half (29%) had written records indicating that they had received all the required doses of the four vaccines. Vaccination information based on provider records was obtained for the other half (30%). These provider data were used to adjust responses for the entire survey group.
A 12-month estimate of vaccination coverage levels was obtained from the four consecutive quarters from July 1994 to June 1995.
Compared with the previous reporting period (from April 1994 to March 1995), statistically significant increases were reported in vaccination with three or more doses of poliovirus vaccine (from 84% to 86%) and with three or more doses of hepB vaccine (42% to 51%).
Coverage rates for DTP/DT, Hib, MMR and the combined series (4:3:1 — four doses of DTP, three doses of poliovirus vaccine, one dose of MMR; and 4:3:1:3 — four doses of DTP, three doses of poliovirus vaccine, one dose of MMR, and three doses of Hib) remained stable.
With coverage at 89% during the survey period, the MMR vaccine was the only vaccine that did not meet the CII's recommended 1995 coverage level of 90%.
State-specific estimated coverage levels for the 4:3:1 series averaged 77%; for the 4:3:1:3 series, coverage levels averaged 75%. Among selected urban areas, coverage levels averaged 76% for the 4:3:1 series and 72% for the 4:3:1:3 series. The CII has not established a coverage goal for either series.
All states, the District of Columbia, and all except one of the 27 urban areas met the CII's 1995 interim goal for coverage with three or more doses of DTP. Forty-nine states and 24 urban areas met the goal for vaccination with three or more doses of Hib. Thirty-one states and 16 urban areas met the CII goal for vaccination with three or more doses of poliovirus vaccine. Twenty-five states and 16 urban areas met the goal for coverage with one or more doses of MMR vaccine. Twenty states and 16 urban areas met the coverage goal with three or more doses of hepB vaccine.
Compared with the previous 12-month estimates, the 1994-1995 national vaccination coverage estimates either increased or remained stable. Most estimates met or surpassed the 1995 goals of the CII.
The coverage goals for 1996 are substantially higher for all vaccines except MMR. To improve coverage and meet these goals, health care providers should check the vaccination status of children who come under their care for other reasons. Other strategies include linking vaccination to the Special Supplemental Nutrition Program for Women, Infants and Children (WIC), and increased and enhanced use of a national vaccination database.
- CDC. National, state and urban area vaccination coverage levels among children aged 19-35 months - United States, July 1994-June 1995. MMWR Special Report. 1996;45:508-512.
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