Containment of polioviruses after eradication and OPV cessation: characterizing risks to improve management.
ABSTRACT The goal of the World Health Organization is to stop routine use of oral poliovirus vaccine shortly after interruption of wild poliovirus transmission. A key component of this goal is to minimize the risk of reintroduction by destruction of polioviruses except in an absolute minimum number of facilities that serve essential functions and implement effective containment. Effective containment begins with a complete facility risk assessment. This article focuses on characterizing the risks of exposure to polioviruses from the essential vaccine production, quality control, and international reference and research facilities that remain. We consider the potential exposure pathways that might lead to a poliovirus reintroduction, including para-occupational exposures and releases to the environment, and review the literature to provide available estimates and a qualitative assessment of containment risks. Minimizing the risk of poliovirus transmission from a poliovirus facility to increasingly susceptible communities is a crucial and ongoing effort requiring understanding and actively managing the potential exposure pathways.
Article: The case for cooperation in managing and maintaining the end of poliomyelitis: stockpile needs and coordinated OPV cessation.[show abstract] [hide abstract]
ABSTRACT: Achieving successful eradication of a disease requires global cooperation to obtain a shared goal. Coordination of the endgame may seem an obvious requirement for success, but that does not ensure that cooperation will occur. To analytically explore the need for cooperation to maintain global polio eradication specifically related to creation of a global polio vaccine stockpile and coordination of oral poliovirus vaccine (OPV) cessation. Using risk and decision analysis and game theoretical concepts, we modeled the importance of global cooperation in managing the risks associated with polioviruses for a time horizon of 20 years after successful global disruption of circulation of wild polioviruses. Countries may wish to avoid the financial costs of vaccination and risks for vaccine-associated paralytic polio following eradication of wild polioviruses, which may lead them to reduce their use of OPV. However, reducing or stopping vaccination too soon and without coordination poses serious risks, including the possibility of reimportation of wild polioviruses and the possibility of vaccine-derived polioviruses. Analysis of the risks for potential outbreaks suggests the need for creation and maintenance of a global stockpile of vaccine for outbreak response. Game theoretical considerations show that coordination of OPV cessation optimizes expected costs and risks globally, despite the potential perceived incentives for countries to stop OPV earlier or later than other countries, or to continue OPV use indefinitely. This article makes the strong case for global cooperation on risk management and suggests that even though individual countries may perceive their own risks as small, risks at the global level warrant cooperative action and coordination of OPV cessation.Medscape journal of medicine 02/2008; 10(8):190.
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ABSTRACT: Eight outbreaks of paralytic polio attributable to circulating vaccine-derived poliovirus (cVDPV) have highlighted the risks associated with oral poliovirus vaccine (OPV) use in areas of low vaccination coverage and poor hygiene. As the Polio Eradication Initiative enters its final stages, it is important to consider the extent to which these viruses spread under different conditions, so that appropriate strategies can be devised to prevent or respond to future cVDPV outbreaks. This paper examines epidemiological (temporal, geographic, age, vaccine history, social group, ascertainment), and virological (type, genetic diversity, virulence) parameters in order to infer the numbers of individuals likely to have been infected in each of these cVDPV outbreaks, and in association with single acute flaccid paralysis (AFP) cases attributable to VDPVs. Although only 114 virologically-confirmed paralytic cases were identified in the eight cVDPV outbreaks, it is likely that a minimum of hundreds of thousands, and more likely several million individuals were infected during these events, and that many thousands more have been infected by VDPV lineages within outbreaks which have escaped detection. Our estimates of the extent of cVDPV circulation suggest widespread transmission in some countries, as might be expected from endemic wild poliovirus transmission in these same settings. These methods for inferring extent of infection will be useful in the context of identifying future surveillance needs, planning for OPV cessation and preparing outbreak response plans.PLoS ONE 02/2008; 3(10):e3433. · 4.09 Impact Factor
Article: Systematic review of mucosal immunity induced by oral and inactivated poliovirus vaccines against virus shedding following oral poliovirus challenge.[show abstract] [hide abstract]
ABSTRACT: Inactivated poliovirus vaccine (IPV) may be used in mass vaccination campaigns during the final stages of polio eradication. It is also likely to be adopted by many countries following the coordinated global cessation of vaccination with oral poliovirus vaccine (OPV) after eradication. The success of IPV in the control of poliomyelitis outbreaks will depend on the degree of nasopharyngeal and intestinal mucosal immunity induced against poliovirus infection. We performed a systematic review of studies published through May 2011 that recorded the prevalence of poliovirus shedding in stool samples or nasopharyngeal secretions collected 5-30 days after a "challenge" dose of OPV. Studies were combined in a meta-analysis of the odds of shedding among children vaccinated according to IPV, OPV, and combination schedules. We identified 31 studies of shedding in stool and four in nasopharyngeal samples that met the inclusion criteria. Individuals vaccinated with OPV were protected against infection and shedding of poliovirus in stool samples collected after challenge compared with unvaccinated individuals (summary odds ratio [OR] for shedding 0.13 (95% confidence interval [CI] 0.08-0.24)). In contrast, IPV provided no protection against shedding compared with unvaccinated individuals (summary OR 0.81 [95% CI 0.59-1.11]) or when given in addition to OPV, compared with individuals given OPV alone (summary OR 1.14 [95% CI 0.82-1.58]). There were insufficient studies of nasopharyngeal shedding to draw a conclusion. IPV does not induce sufficient intestinal mucosal immunity to reduce the prevalence of fecal poliovirus shedding after challenge, although there was some evidence that it can reduce the quantity of virus shed. The impact of IPV on poliovirus transmission in countries where fecal-oral spread is common is unknown but is likely to be limited compared with OPV.PLoS Pathogens 04/2012; 8(4):e1002599. · 9.13 Impact Factor