Measuring Immunization Coverage: What Best Reflects the Protection of Children?

Background:
Background: The National Immunization Survey (NIS) has assessed the rates for cumulative completion of immunization for American children since 1994.

Objectives:
To compare NIS data for the 4:3:1:3:3:1 cumulative series for 2006 (the “UTD-all-series method”) with averaged data for individual vaccine series (for DTaP, polio, MMR, Hib, and hepatitis B and varicella). This latter method was called the “disease-protected method” since it better reflects protection from vaccine-preventable disease.

Methods:
Mathematical calculation of averaged data for each state and comparison with reported cumulative UTD rates.

Results:
The disease-protected method was 14.1 percentage points higher than UTD-all-series. 77.0% of children in the United States are completely vaccinated for all vaccine series. 91.1% of all vaccine series have been completed. The 4:3:1:3:3:1 method provides an accurate estimate of the percentage of children that need one or more additional vaccine. The disease-protected method of evaluating NIS data provides an accurate assessment of protection of children against vaccine-preventable diseases. Assuming that completion of a vaccine series implies protection against disease, children in the United States are protected against 91% of vaccine preventable diseases, although only 77% have completed all doses of all vaccine series.

Conclusions:
The UTD-all-series method and the disease-protected method provide different forms of information about vaccination and should both be provided in the publication of NIS data.