The World Health Organization says many governments report incorrect information about the number of children vaccinated for common diseases. It says the estimates are usually exaggerated and while the errors are generally unintentional, they are misleading about how well a country is controlling infections.
According to a World Health Organization survey of 45 developing nations, national health programs usually report that more children have been vaccinated effectively than is really the case.
The survey director, WHO physician Bakhuti Shengelia of Georgia, says inaccurate assessments of inoculation rates undermine national health programs.
"We need to help the countries that are struggling with communicable and childhood diseases," he said. "Therefore, the validity of the evidence is important in order to understand how well we are doing in terms of controlling infectious diseases among children in order to reduce child mortality and improve the quality of life."
In a report in the medical journal The Lancet, Dr. Shengelia and colleagues focused on the use of the diptheria-tetanus-pertussis shot in the 45 countries as an indicator of overall vaccination coverage. They compared officially reported data about coverage with this DPT vaccine to answers from household questionnaires in the decade of the 1990s. The household surveys are considered very accurate because they were taken under WHO guidelines soon after the shots were given.
The results show that about three-fourths of the governments reported DPT vaccine coverage to be at least 10 percent higher than the households reported. In about half the cases, it was 20 percent higher. In some countries, however, vaccine coverage was under-reported.
The WHO investigators suggest that the differences occurred because of weak health information systems and the presence of incentives for over-reporting. In the cases where too few vaccinations were reported, the governments did not sufficiently account for inoculations provided by private-sector health workers.
Dr. Shengelia says another reason for the discrepancy is that governments often measure all vaccinations that take place, even those not delivered according to the World Health Organization schedule and, therefore, not effective in preventing disease.
"For policymakers, probably what matters is to put more attention and emphasis on the valid immunizations as a measure of the performance of immunization programs," he said.
The investigators recommend that governments supplement their official statistics with data from other sources.
"Countries need to strengthen their health information systems so that they include various sources like household surveys [and] statistics from the delivery network so that the final information that is available for program managers and policymakers is valid and reflects the realities," he said.
Dr. Shengelia says the World Health Organization is engaged in a major effort to improve the quality of such evidence so health ministries can direct scarce resources better.