Vaccinating against the infectious diseases of poverty: do national programmes over-estimate their achievements?

22 Dec 2008

Paul Chinnock

Source: Lancet (see original article)

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Children queuing to be vaccinated in Côte d’Ivoire. WHO.

There are now effective vaccines available against several of the biggest infectious killers of children and more are in the pipeline. But how effective are national programmes in getting these vaccines to the children who need them? It is vital that reliable information on this point should be available, but a new study published in the Lancet casts doubts on the accuracy of official statistics.

As a long established vaccine, DTP3 (i.e. three doses of vaccine for diphtheria, tetanus, and pertussis), provides a useful marker for how programmes are faring. Researchers from the Institute for Health Metrics and Evaluation, University of Washington, estimated DTP3 coverage by analysing data from over 600 household surveys conducted in 193 countries. They found an encouraging increase in coverage from 59% in 1986 to 79% in 2006). However, the correlation between survey data and official reports was poor. Sometimes the survey data indicated that fewer children had been vaccinated than had been reported and sometimes more, but over-reporting of coverage rates by official sources was more common especially in recent years.

One reason that the situation is so worrying concerns the possible influence of the Global Alliance on Vaccines and Immunisations (GAVI), the public–private partnership that aims to increase coverage of basic vaccines and to accelerate the introduction of new vaccines in low-income countries. Launched in 1999, GAVI pays countries proportionally to the number of children they have vaccinated with DTP3. From their analysis, the authors conclude that in some countries this performance-based payment system seems to be associated with over-reporting of the performance indicator – i.e. the number of children immunised.

Could it therefore be that financial incentives to report DTP3 coverage are biasing official reports?

Summing up the implications of their findings, the researchers say: “Survey-based DTP3 immunisation coverage has improved more gradually and not to the level suggested by countries’ official reports or WHO and UNICEF estimates. There is 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.”

These authors are not the first to cast doubt on the wisdom of the target-setting and performance-based systems, which are now common place in public health programmes of many types worldwide. However, there has so far been a lack of evidence to inform debate on the issue and these new findings are likely to be of widespread interest.

A commentary on the article, written by David Bishai of Johns Hopkins Bloomberg School of Public Health, is published in the same issue of the journal.