A Dynamic Model of Poliomyelitis Outbreaks: Learning from the Past to Help Inform the Future

Abstract

Policy-makers now face important questions regarding the tradeoffs among different strategies for managing poliomyelitis risks after they succeed with polio eradication. To estimate the potential consequences of reintroductions of polioviruses and the resulting outbreaks, the authors developed a dynamic disease transmission model that can simulate many aspects of outbreaks for different posteradication conditions. In this paper, the authors identify the issues related to prospective modeling of future outbreaks using such a model, including the reality that accurate prediction of conditions and associated model inputs prior to future outbreaks remains challenging. The authors explored the model's behavior in the context of three recent outbreaks resulting from importation of poliovirus into previously polio-free countries and found that the model reproduced reported data on the incidence of cases. The authors expect that this model can provide important insights into the dynamics of future potential poliomyelitis outbreaks and in this way serve as a useful tool for risk assessment.

Expert Review on Poliovirus Immunity and Transmission

“…Modeling poliovirus transmission requires characterization of the population immunity as it evolves over time for each of the three serotypes . For polioviruses, the large number of combinations of potential types of individual immunity complicates the characterization of population immunity .…”

“…As a result of the complexity of immunity, poliovirus infection transmission models must go beyond simple susceptible‐infected‐removed (SIR) models . While we recognize that the ability to participate in poliovirus transmission depends on many factors besides immunity, such as contact patterns and environmental conditions, we focus this review on the role of immunity and we assume that risk and policy models will capture the other factors in the basic reproductive number ( R 0 ) or more detailed characterizations of mixing . Thus, for this review determining the specific immunity states used to characterize population immunity represents the first task in model development …”

“…A large number of complex policy decisions to manage risks before WPV eradication and beyond motivate the use of models to understand the tradeoffs between alternatives and quantify the impact of different assumptions on outcomes. Dynamic infection transmission models combined with probabilistic risk analyses can provide projections of disease burden anticipated with different courses of action . These projections represent critical inputs to health economic analyses, such as cost‐effectiveness analyses and benefit‐cost analyses, that aim to inform decisions by evaluating the benefits, risks, and costs of alternative options and providing insights about tradeoffs .…”

The probability of undetected wild poliovirus circulation: Can we do better?

“…These global successes, suggesting that the endgame is near, have been achieved by the use of two different polio vaccines (Duintjer Tebbens et al, 2005): inactivated poliovirus vaccine (IPV) and oral poliovirus vaccine (OPV). IPV is relatively harder to administer since it requires an injection and comes at a higher price than OPV that consists in simply two drops taken orally (Duintjer Tebbens et al, 2010).…”

“…Moreover, OPV contains a live attenuated virus that provides immunity to symptomatic polio and better protection against intestinal reinfection than IPV (Duintjer Tebbens et al, 2013a). The attenuated virus contained in OPV can also spread to others and provide secondary immunity (Duintjer Tebbens et al, 2005;Onorato et al, 1991). However, as the live attenuated virus included in OPV circulates, it can undergo genetic mutations.…”