Avoiding the Will O’ the Wisp: Challenges in Measuring High Levels of Immunization Coverage with Precision

David W Brown,Marta Gacic-Dobo,Anthony H Burton,Griffith Feeney

doi:10.4236/wjv.2014.43012

Abstract

There have been tremendous improvements in immunization coverage since the Expanded Programme on Immunization was launched. We highlight inherent challenges in measuring immunization coverage with precision as coverage levels increase due to the sensitivity of coverage to the accuracy of target population estimates. In fact, when comparing across groups at high levels of coverage, error in target population estimates can obscure differences in immunization coverage.

Highlights

Immunization coverage levels are presented as the percentage of a target population that has been vaccinated
A review of the Table 1 shows that when true coverage is 50% (Country C), for example, 50 of the 100 children in the target population are vaccinated, but coverage calculated from the estimated target population may be as low as 45% (50/110) or as high as 56% (50/90), the range shown in Column (6)
When one looks at the upward trend in coverage across countries in the Figure 1, coverage level increases from 10% to 20% which are not obscured by the error in the target population estimate

Summary

Introduction

When the Expanded Programme on Immunization was launched in 1974, less than 5% of the world’s children were immunized during their first year of life against polio, diphtheria, tuberculosis, pertussis, measles and tetanus [1]. Even in the presence of perfect recording and monitoring of the number of children vaccinated, there are inherent challenges in measuring immunization coverage with precision as coverage levels increase due to the sensitivity of coverage to the accuracy of target population estimates. Immunization coverage levels are presented as the percentage of a target population that has been vaccinated.

Results

Conclusion