Research conducted at IHME examines the number of children receiving diphtheria, tetanus, and pertussis (DTP3) immunizations in 193 countries from 1986 to 2006. The study, Tracking progress towards universal childhood immunisation and the impact of global initiatives: a systematic analysis of three-dose diphtheria, tetanus, and pertussis immunisation coverage, reveals troubling gaps between the number of children reported by countries to be immunized and numbers based on independent surveys in countries receiving aid money from the GAVI Alliance Services Support (ISS) program.
The researchers found that while there have been continual improvements globally in the proportion of children immunized against DTP3, this has increased only gradually over time and not to the level suggested by countries’ official reports. For example, since the launch of GAVI in 1999, officially-reported estimates showed a 9% increase in DTP3 coverage, from 81% to 90%, while survey-based estimates only showed a 4.9% increase in global coverage, from 69% to 74%, over the same period.
The study also found that the GAVI ISS program, which pays countries US $20 for each additional child that countries report to have immunized, leads to overreporting in more than half of countries. Of 51 countries receiving ISS funding from GAVI, six countries overestimated the additional number of children immunized by four times, 10 countries overestimated their increase in coverage by more than double, 23 countries overestimated by less than double, and eight countries underestimated their increase in the number of children immunized.
The gap between country-reported data and independent survey data was particularly wide in the Democratic Republic of the Congo, Guinea, Liberia, Mali, Niger, and Pakistan. In some of these countries, such as Niger and Mali, officially reported DTP3 coverage was almost 100%, while survey data for these countries showed that immunization coverage was closer to 50%.
Overall, in the countries receiving ISS funding from GAVI, countries reported immunizing 13.9 million additional children, while independent surveys showed only 7.4 million additional children were immunized. At a rate of US $20 per additional child immunized, GAVI disbursed performance-based payments of $290 million, while the analysis showed survey-based estimated payments should have been $150 million, a difference of $140 million.
Researchers estimated DTP3 coverage by analyzing unit record data from surveys and supplemented this with reported coverage from other surveys and administrative data. They used bidirectional distance-dependent regression to estimate trends in survey-based coverage in 13 countries during 1986 to 2006. They then used standard time series cross-sectional analysis to investigate any association in the difference between countries’ official reports and survey-based coverage and the presence of GAVI ISS, controlling for country and time effects.
Substantial resources have been invested in increasing childhood immunization coverage through global initiatives such as the Universal Childhood Immunization campaign and GAVI. Concerns have been raised about how target- and performance-oriented initiatives might encourage overreporting. The researchers thus aimed to evaluate the coverage of the DTP3 vaccine based on surveys using all available data. This research is part of ongoing work by IHME to track the performance of societies in addressing health challenges.
Recommendations for future work
The findings from this study highlight an urgent need for independent and contestable monitoring of health indicators in an era of global initiatives that are target-oriented and disburse funds based on performance.