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Fight Against Measles Appears Stalled
23 April 2012 6:30 pm
Measles deaths dropped dramatically in the first decade of the 21st century, but progress has stalled since 2007, new estimates show. A report from the World Health Organization (WHO), the U.S. Centers for Disease Control and Prevention (CDC), and Pennsylvania State University calculates that global measles deaths fell from 535,000 in 2000 to 139,000 in 2010—an impressive 74% reduction, but short of WHO's goal of 90%. More worryingly, the paper, released in The Lancet today, shows that those numbers have essentially remained flat since 2007.
The measles virus is one of the deadliest pathogens in human history. Infection leads to a prolonged weakening of the immune system, and most deaths are due to secondary bacterial or viral infections. Particularly in poor countries, up to one in 10 infected children die of the disease. Before a vaccine became available in 1963, more than 2 million children are estimated to have succumbed to the disease each year; today, more than 100,000 children still die every year because they haven't been adequately vaccinated.
In 2001, WHO, CDC, the American Red Cross, and others formed a new partnership called the Measles Initiative to provide the measles vaccine to all children through mass vaccination campaigns and strengthening of routine immunization. The two doses needed, usually one before the child's first birthday and one in the next few years, cost less than $1. And in 2008, WHO adopted a goal of reducing global measles deaths by 90% by 2010, compared with 2000.
To assess whether that was achieved, the authors of The Lancet paper used a new statistical method. Earlier research had relied on data about vaccine coverage and effectiveness to estimate measles deaths. Scientists usually calculated how many people were susceptible to measles and then essentially assumed that all of them would catch measles. For the new report, the researchers integrated surveillance data showing how measles infections fluctuate from year to year. "This allows us to capture the boom-bust nature of measles outbreaks," says co-author Peter Strebel, a measles expert at WHO. It also accounts better for herd immunity, the fact that as vaccination rates go up, unvaccinated people are somewhat protected by other people's vaccinations. The resulting numbers are lower than earlier estimates. For instance, the study puts the 2000 toll at 535,000, almost 200,000 lower than previous calculations. "These are the best estimates we have ever had," Strebel says.
But because many countries have little surveillance data available, the statistical uncertainty is still huge, ranging from 71,000 to 447,000 deaths for the year 2010. "It is clear that we need to move beyond these estimates and develop systems in these countries that measure deaths," says Walter Orenstein, an immunologist from Emory University in Atlanta. This would be a crucial prerequisite for any plan to eradicate measles, he suggests.
Even with this uncertainty, however, it seems clear that the fight against measles has stalled since 2007. "The primary reason is the global recession, which led to a 75% decrease in funding for the measles initiative," says Stephen Cochi, a pediatrician at CDC, who was not involved in The Lancet study. Vaccination campaigns were delayed, corners were cut, and target groups were narrowed, he says.
The new numbers also put the spotlight on India. Overall, the country showed the smallest reduction in deaths, which dropped from 88,000 in 2000 to just 66,000 in 2010, and India now accounts for almost half the measles deaths in the world. But India only recently introduced a second dose of measles vaccine to its routine immunization schedules. "They started very late," says Strebel. "But they have made great progress in 2011 and 2012 that is not yet captured in the data."
Cochi is confident that measles mortality will drop further in the coming years. "Funding has improved again and we are anticipating a big reduction in measles mortality in India, which will have a big impact on the global curve," he says. WHO is certainly gunning for it. In a new strategic plan for measles for 2012 to 2020, the organization set the goal of reducing the incidence of measles to less than five cases per million by 2015 and establishing a target date for the global eradication of measles by then, as well. WHO also wants to tackle rubella and measles together. "A three-quarters drop in measles deaths worldwide shows just how effective well-run vaccination programmes can be," said WHO Director-General Margaret Chan in a press release. "Now we need to take the next logical step and vaccinate children against rubella, too."