now you see ... [1945015vaccination] Ring seemed to have a dramatic effect on a chart published in 1971 and 1975 ( top ) - but not in a new Kaplan analysis ( down ).
a new look at two-decades-old studies could have important consequences for US policy smallpox, according to a paper in the January issue of epidemiology . The study challenges a key element of proof of the effectiveness of the "ring vaccination" a cornerstone of the US plan to contain smallpox outbreaks. But the authors of the original documents say that even if the study is right, there are a lot of other evidence that ring vaccination works.
Last month, the Bush administration announced it would vaccinate up to 11 million people preemptively against smallpox ( science NOW, December 13, 02). But postattack game plan is still evolving. The current version features prominently ring vaccination -. Isolate victims of smallpox and quickly immunizing all their close contacts, and the contacts of these people
In the new document, mathematician Edward Kaplan of Yale University and colleagues aim to chart, published in scientific articles in 1971 and 1975, claiming that ring vaccination was highly effective in the global campaign to eradicate smallpox. The figure submitted by an officer of the Centers for Disease Control and Prevention on several key policy meetings last year, seems to show a sharp drop in new cases just after the ring vaccination was introduced in 20 countries in West and Central Africa September 1968.
But Kaplan said the character uses several tricks to make its case. For example, using inappropriately a logarithmic scale on the Y axis, the authors exaggerate the fall in incidence, while portraying the gains in overall immunization coverage (percentage of unvaccinated people descending) between January 1968 and in March 1969 as banal. In fact, says Kaplan, the vaccination rate has tripled during this period. When Kaplan reanalyzed the data and plot the actual number of cases and the percentage of unvaccinated people over time on an arithmetic scale, the two appeared to decrease at the same rate; nothing notable happened shortly after ring vaccination began.
William Foege, the first author on the two previous articles and now a consultant to the Bill and Melinda Gates Foundation, is at the figure, arguing that the logarithmic plots are perfectly acceptable in epidemiological graphics. But Donald A. Henderson, the former head of the eradication campaign and a co-author on the 1975 paper, concedes it has been established with a political goal: convince reluctant governments in developing countries adopt ring vaccination. "I've always had trouble with that curve myself," said Henderson.
Both agree, however, that focusing on the graph, Kaplan ignores a wealth of evidence that ring vaccination worked. In March 1969, not more than 60% of the population in West and Central Africa have been vaccinated - which in normal circumstances would never be enough to erase smallpox, said Foege. Even in India, where coverage reached more than 0%, the plague kept festering in some areas, he added. Once the ring vaccination was introduced, it was gone in a year. "Kaplan does not understand what he's talking," says Henderson.
Related Sites
Smallpox Preparedness and Response Activities CDC
The homepage of Edward Kaplan
0 Komentar