Eradication Versus Control for Poliomyelitis: An Economic Analysis
by Kimberly M. Thompson and Radboud J. Duintjer Tebbens, The Lancet 2007;369:1363-1371

Press release - April 11, 2007
Press coverage - Media coverage of this study included an article written by Leslie Roberts in Science Magazine, and John Donnelly's Boston Globe article that followed presentation of the study's preliminary results at a WHO urgent stakeholder consultation in February 2007. In July 2008, this paper won the Jay Wright Forrester Award for the best contribution to the field of System Dynamics during the preceding five years.

Answers to frequently asked questions -

What are the study’s main findings?
What are the study’s main recommendations?
What do the cost-effectiveness ratios mean in this paper?
How much will polio eradication actually cost?
Is global polio eradication feasible?
What is immunization intensity?
Why are the costs of control in the endemic areas so high for every modeled control option?
Background on polio

What are the study’s main findings?

  • 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 polioviruses to continue to circulate-which proponents of control believe can sustain the low number of cases. This paper urges explicit consideration of the health and financial trade-offs associated with this choice.
  • Comparing the numbers of expected cases and costs for 20 years into the future for a range of eradication and control options, the study finds that eradication is the best solution. 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.
  • The results suggest that control means a future with high costs and low cases or with low costs and high cases. Low costs and low cases is only an option if we continue to pay high costs in the short-term until we eradicate.
  • Results from a dynamic model of endemic wild poliovirus transmission in the populous Northern India states of Uttar Pradesh and Bihar show that eliminating the virus requires that we increase the immunization intensity.
  • Permanently reducing vaccination intensity even by a small percentage will lead to a significant resurgence of polio incidence and thousands of annual cases expected just in Uttar Pradesh and Bihar.
  • This study demonstrates that acting based on concerns of incurring high costs to prevent few polio cases will eventually lead to more polio cases and much higher cumulative costs compared to eradication followed by cessation of vaccination. A wavering commitment to eradication is not a good option.
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What are the study’s main recommendations?
  • We should require stakeholders in the debate about whether to give up or pursue the current option to eradicate polio to make their assumptions about costs and cases of specific options explicit and transparent.
  • We need to take a long-term perspective with respect to decisions about global polio eradication. Failing to do so will not only put children in developing countries at a higher risk of getting polio, but in the long term will also hurt other public efforts in those countries.
  • Discussions about opportunity costs should consider the opportunity costs that we will incur if we do not eradicate polio, which will include real children paralyzed by the disease (predominantly in low-income countries that already suffer from large disease burdens) and real resources that we will continue to spend on polio control in perpetuity that cannot be used for other public health interventions.
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What do the cost-effectiveness ratios mean in this paper?
  • This paper sought to expose the weakness of thinking in terms of high costs aimed at a disease with a now very low global number of reported cases, which is the way that some non-economists appear to be looking at the current situation for polio. To demonstrate this, this paper modeled what would happen if we based decisions on a na´ve understanding of cost-effectiveness ratios formulated as costs per case. The demonstrative example in the paper shows that basing decisions on a concern about high costs per case would result in a failure to complete eradication, and ultimately yield higher costs and more polio cases due to a wavering commitment. This problem is one reason why economists use costs per case prevented for cost-effectiveness ratios.
  • In the analysis for all of the low-income group countries, the study notably does not present incremental cost-effectiveness ratios. However, Figure 5 shows the costs and cases of the various eradication and control options from which these could be derived. The costs of achieving eradication are unknown and as stated in the paper they are not included. Instead, the study focuses on estimating the amount that we should be willing to spend to achieve eradication. The results of the analysis of the amount that we should be willing to pay to eradicate results can be correctly interpreted as showing that from an incremental cost-effectiveness perspective eradication dominates control as long as the costs of eradication are less than a minimum of $3 billion ($2 billion if we completely ignore treatment costs and outcomes in middle-income countries). In addition, since all of the eradication scenarios yield fewer cases than the control options (except for the bad option of OPV without supplemental immunization activities after eradication vs. high control options), we would obtain negative denominators and thus negative and non-standard incremental cost-effectiveness ratios (implying that we would save money to suffer worse health outcomes). (We also estimated incremental cost-effectiveness ratios and incremental net benefits for future polio risk management policies.)
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How much will polio eradication actually cost?
  • We do not know the costs needed to finish eradication or the time required, although with very few areas remaining endemic so long as we sustain the commitment eradication appears close.
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Is global polio eradication feasible?
  • One of the three wild poliovirus serotypes (type 2) was eradicated globally in 1999. The GPEI has demonstrated the ability to interrupt wild poliovirus in some of the most challenging regions, including areas with high population density, poor sanitation, almost no public health infrastructure, and civil or military conflict.
  • This paper assumes that "eradication is achievable provided that we are willing to commit the necessary resources."
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What is immunization intensity?
  • Immunization intensity is an indication of the level of effort aimed at increasing population immunity. We define immunization intensity specifically as the fraction of susceptible people who become immune because of exposure to oral vaccine viruses per year (i.e., from successful routine or supplemental oral poliovirus vaccination, or secondary exposure to oral poliovirus vaccine).
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Why are the costs of control in the endemic areas so high for every modeled control option?
  • The study assumes that the control policies would involve sufficient resources to effectively maintain the current incidence of approximately 1,300 paralytic polio cases per year in endemic areas. If not, we will likely see a rapid expansion of the endemic areas and more frequent importation outbreaks into countries that are now free of wild poliovirus transmission.
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