Eradicating polio a better option than extended control of the disease

Apr 15 2007

Concerns about the high perceived costs of eradicating the relatively low number of polio cases worldwide have led to recent suggestions that it is time to shift from a goal of eradication to control—abandoning eradication and allowing wild poliovirus to continue to circulate, which proponents of control believe can sustain the low number of cases.

In a new study, researchers from the Harvard School of Public Health (HSPH) analyzed the costs and health outcomes of control and eradication options. They found that the relatively high short-term costs of global polio eradication will ultimately be much lower than the long-term financial and human health costs required to control polio forever. The study appears online April 11 and in the April 21, 2007 print issue of The Lancet.

Poliomyelitis, which mainly affects children, is a highly infectious viral disease that can cause inflammation of motor neurons of the brainstem and spinal cord and lead to paralysis. Although successfully eliminated in the U.S. and most of the world through the use of poliovirus vaccines, endemic wild polioviruses still continue to circulate in some countries (notably in parts of India, Nigeria, Pakistan and Afghanistan). Since 1988, the Global Polio Eradication Initiative has reduced the global incidence of poliomyelitis by 99%, at a cost of more than $4 billion.

Kimberly Thompson, Associate Professor of Risk Analysis and Decision Science at HSPH, and Radboud Duintjer Tebbens, a research associate at HSPH, used a mathematical model to demonstrate the importance of maintaining and increasing the immunization intensity in currently endemic areas. Immunization intensity is an indication of the level of vaccination effort aimed at increasing population immunity. The authors suggest that even a relatively small decrease in intensity of immunization could lead to relatively large outbreaks. They emphasized that the world cannot let up in its vaccination efforts for polio, at least until eradication has been achieved.

Comparing the numbers of expected cases and costs for 20 years into the future for a range of eradication and control options, the authors found that eradication is the best solution. For example, a control policy that relied only on routine immunization could lead to approximately 200,000 expected paralytic polio cases every year in low-income countries. “As long as it is technically achievable, eradication offers both lower cumulative costs and cases than control in the long-term, even with the costs of achieving eradication exceeding several billion dollars more,” said Thompson.

The authors note in the study that debate about eradication versus control should include careful consideration of the trade-offs of the options. “Control means high costs and low cases forever or low costs and high cases forever, but not low costs and low cases forever, which is only an option if we continue to pay high costs in the short-term until we eradicate,” said Thompson.

Although the price tag of potentially additional billions of dollars to eradicate polio may sound high, the study reports that paying now is the best way to keep the overall costs as low as possible. “A wavering commitment to eradication is not a good option,” said Duintjer Tebbens.

(Thompson and Duintjer Tebbens recently estimated that the net benefits of polio vaccinations in the U.S. alone exceed $180 billion. To view a copy of that press release, go to http://www.hsph.harvard.edu/news/press-releases/2007-releases/press01192007.html).

“Eradication Versus Control for Poliomyelitis: An Economic Analysis,” Kimberly M. Thompson, Radboud J. Duintjer Tebbens, The Lancet , online April 11, 2007.

Support for this study was provided by the Kids Risk Project at the Harvard School of Public Health. (http://www.kidsrisk.harvard.edu/). Other polio-related studies by the authors have received support from the U.S. Centers for Disease Control and Prevention.

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