An economic analysis of poliovirus risk management policy options for 2013–2052

Abstract

BackgroundThe Global Polio Eradication Initiative plans for coordinated cessation of oral poliovirus vaccine (OPV) after interrupting all wild poliovirus (WPV) transmission, but many questions remain related to long-term poliovirus risk management policies.MethodsWe used an integrated dynamic poliovirus transmission and stochastic risk model to simulate possible futures and estimate the health and economic outcomes of maintaining the 2013 status quo of continued OPV use in most developing countries compared with OPV cessation policies with various assumptions about global inactivated poliovirus vaccine (IPV) adoption.ResultsContinued OPV use after global WPV eradication leads to continued high costs and/or high cases. Global OPV cessation comes with a high probability of at least one outbreak, which aggressive outbreak response can successfully control in most instances. A low but non-zero probability exists of uncontrolled outbreaks following a poliovirus reintroduction long after OPV cessation in a population in which IPV-alone cannot prevent poliovirus transmission. We estimate global incremental net benefits during 2013–2052 of approximately $16 billion (US$2013) for OPV cessation with at least one IPV routine immunization dose in all countries until 2024 compared to continued OPV use, although significant uncertainty remains associated with the frequency of exportations between populations and the implementation of long term risk management policies.ConclusionsGlobal OPV cessation offers the possibility of large future health and economic benefits compared to continued OPV use. Long-term poliovirus risk management interventions matter (e.g., IPV use duration, outbreak response, containment, continued surveillance, stockpile size and contents, vaccine production site requirements, potential antiviral drugs, and potential safer vaccines) and require careful consideration. Risk management activities can help to ensure a low risk of uncontrolled outbreaks and preserve or further increase the positive net benefits of OPV cessation. Important uncertainties will require more research, including characterizing immunodeficient long-term poliovirus excretor risks, containment risks, and the kinetics of outbreaks and response in an unprecedented world without widespread live poliovirus exposure.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-015-1112-8) contains supplementary material, which is available to authorized users.

Polio endgame risks and the possibility of restarting the use of oral poliovirus vaccine

“…However, as population immunity to transmission declines following OPV cessation, any remaining iVPDVs excreted may begin to cause transmission in the surrounding communities [38]. Finally, the risk of (un)intentional releases from vaccine manufacturing sites or laboratories handling poliovirus-containing materials remains a continuing source of potential outbreaks after cessation [39,40]. …”

“…We integrated the risk estimates with economic [42] and dynamic transmission models [43] into a global model for long-term poliovirus risk management [40]. The global model yielded estimates of aggregate health and economic outcomes of major immunization policy choices [40] assuming ideal implementation of risk management strategies, including aggressive outbreak response [44] and OPV intensification wherever needed to prevent post-cessation cVDPV outbreaks [26]. Subsequent publications using the global model considered the impact of specific risk management strategies [7,38,45] and the implications of non-synchronous OPV cessation or subsequent unauthorized OPV use [18,46,47].…”

“…the risk management prevented them) or stop following an aggressive outbreak response [40,44]. However, the model suggested that if iVDPV or other live poliovirus reintroductions occurred long after OPV cessation and/or in places with conditions conducive to intense fecal-oral poliovirus transmission, then this would result in uncontrolled outbreaks and a need to restart OPV in most countries that currently use OPV [40].…”

“…the risk management prevented them) or stop following an aggressive outbreak response [40,44]. However, the model suggested that if iVDPV or other live poliovirus reintroductions occurred long after OPV cessation and/or in places with conditions conducive to intense fecal-oral poliovirus transmission, then this would result in uncontrolled outbreaks and a need to restart OPV in most countries that currently use OPV [40]. Despite the ideal implementation of risk management strategies, the model suggested approximately a 5% chance of needing to restart OPV based on 1,000 stochastic iterations and a somewhat arbitrary threshold of 50,000 post-cessation polio cases used as the trigger to restart OPV use globally [38].…”

“…To summarize the epidemiological situation following OPV2 cessation, we reviewed the experience as of April 2018, and we discuss the evidence in the context of our previously published models. To characterize the risks that may trigger OPV restarts overtime, we complement the existing GPEI post-certification strategic plan [53] with a timeline of the principal outbreak risks for each serotype based on existing global model runs [38,40]. In the context of this analysis, we highlight the limitations of the assumptions in the prior modeling with respect to the implementation of risk management strategies and the likely future polio endgame path.…”