A novel, evidence–based methodology for polio risk assessment – Australia, 2018–2019

  • Public health surveillance
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Poliovirus circulation persists in some of the most underdeveloped and insecure regions of the globe. All polio–free countries remain at risk of polio recurrence until eradication is achieved. In 2014, the World Health Organization (WHO) declared the international spread of poliovirus a Public Health Emergency of International Concern. Under the International Health Regulations (2005), WHO Member States need to verify certification of polio–free status annually. In 2018, Australia sought to reassess and comprehensively characterise the risk posed by wild–type and vaccine–derived polioviruses to national health security. However formal international polio risk assessment guidelines do not exist.

A novel mixed-methods approach was developed to capture key components of likelihood and impact that influence poliovirus reintroduction, outbreak and sustained transmission risk. Four risk elements were identified and weighted using an expert–informed Delphi method: reintroduction hazard (poliovirus importation or laboratory containment failure), population immunity, surveillance quality and performance, and outbreak response capability. Australian data and qualitative evidence were analysed, documented and scored against risk element indicators to characterise polio risk as a semi–quantitative estimate and qualitative risk category.

The semi–quantitative risk characterization estimate calculated to a likelihood and impact score of 0.43 and 0.13, respectively (possible range: 0.02–4.5). The semi–quantitative results translated to a qualitative risk category statement of very low risk.

The assessment concluded that the risk of poliovirus reintroduction, resultant outbreaks of poliovirus infection, and sustained transmission occurring in Australia in the next five years is very low. Until poliovirus is eradicated, it remains in Australia’s strategic health security interest to maintain appropriate investment in the prevention, preparedness, surveillance and response capability which underpins the very low level of risk. Use of a structured, transparent and reproducible methodology simplifies completion of future assessments, generates evidence for targeted investment, and provides a framework to support other countries to evaluate their poliovirus risk.

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