Evaluation of Response Scenarios to Potential Polio Outbreaks Using Mathematical Models
by Kimberly M. Thompson, Radboud J. Duintjer Tebbens, and Mark A. Pallansch, Risk Analysis 2006;26(6):1541-1556

Abstract

Appropriate response to polio outbreaks represents an important prerequisite for achieving and maintaining global polio eradication. We use an existing dynamic disease transmission model to evaluate the impact of different aspects of immunization campaigns in response to polio outbreaks occurring in previously polio-free areas. This analysis yields several important insights about response strategies. We find that delay in response represents a crucial risk factor for occurrence of large outbreaks and we characterize the tradeoffs associated with delaying the initial response to achieve better population coverage. We also demonstrate that controlling most potential outbreaks will likely require at least three immunization rounds, although the impact of the optimal interval between rounds varies. Finally, long after oral poliovirus vaccine cessation the choice of target age groups during a response represents an important consideration.

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What are the study’s main findings?
What are the study’s main recommendations?
Background on polio

What are the study’s main findings?

• Global health leaders will need to maintain polio outbreak response plans and capability into the future, and should with a reasonably high probability expect to use them at least once after successful eradication.
• Dynamic modeling of a large set of outbreak and response scenarios demonstrates the crucial importance of responding fast to outbreaks in order to limit the magnitude of these outbreaks.
• The study indicates that small sacrifices in the coverage of the first immunization response rounds in favor of a faster response will typically result in smaller outbreaks, and provides figures that demonstrate the trade-offs.
• Controlling polio importation outbreaks requires at least three massive immunization rounds.
• For outbreaks occurring long after oral poliovirus vaccine cessation, the choice of target age groups during a response represents an important consideration.
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• After OPV cessation, public health leaders must be prepared to respond to outbreaks with minimal delay to re-interrupt transmission and protect the polio-free state of the world. This insight also influenced pre-eradication policy with respect to encouraging much more rapid response (see page 3).
• Policy makers must carefully consider the costs and benefits of continued high-quality surveillance after OPV cessation to ensure successful control of potential outbreaks.
• Further research is needed to develop adequate outbreak response strategies that minimize the risk that OPV viruses used in outbreak response become sources of VDPVs.
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