Stephen Lim and colleagues from the University of Washington in Seattle, examined diphtheria, tetanus and pertussis immunisation coverage. They compared countries’ official reports with surveys of mothers and of children’s vaccine report cards.
There were large discrepancies between officially reported estimates and their survey-based data. Surveys suggested that coverage may be lower in some countries than official figures suggest and higher in others. For the UK, official figures report 92% coverage, whereas the researchers’ survey-based data suggest coverage of 84%.
The Global Alliance on Vaccines and Immunisations provides countries with payments proportional to the number of vaccinated children, and the authors suggest that this may have led to over-estimates of immunisation coverage.
‘An incentive to over-report progress, whether intentionally or unintentionally, will always exist with performance-based payments,’ they warn. ‘To counter-act this problem requires not only independent monitoring, but also a system that is based on rigorous, empirical measurements using the best scientific methods.’ They suggest that a monitoring system, supported by periodic surveys to provide a benchmark for figures, should be introduced.
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