Expert Review on Poliovirus Immunity and Transmission

Successfully managing risks to achieve wild polioviruses (WPVs) eradication and address the complexities of oral poliovirus vaccine (OPV) cessation to stop all cases of paralytic poliomyelitis depends strongly on our collective understanding of poliovirus immunity and transmission. With increased shifting from OPV to inactivated poliovirus vaccine (IPV), numerous risk management choices motivate the need to understand the tradeoffs and uncertainties and to develop models to help inform decisions. The U.S. Centers for Disease Control and Prevention hosted a meeting of international experts in April 2010 to review the available literature relevant to poliovirus immunity and transmission. This expert review evaluates 66 OPV challenge studies and other evidence to support the development of quantitative models of poliovirus transmission and potential outbreaks. This review focuses on characterization of immunity as a function of exposure history in terms of susceptibility to excretion, duration of excretion, and concentration of excreted virus. We also discuss the evidence of waning of host immunity to poliovirus transmission, the relationship between the concentration of poliovirus excreted and infectiousness, the importance of different transmission routes, and the differences in transmissibility between OPV and WPV. We discuss the limitations of the available evidence for use in polio risk models, and conclude that despite the relatively large number of studies on immunity, very limited data exist to directly support quantification of model inputs related to transmission. Given the limitations in the evidence, we identify the need for expert input to derive quantitative model inputs from the existing data.     

The development of the resource-based view of the firm: A critical appraisal

Over the last 20 years, the resource-based view (RBV) has reached a pre-eminent position among theories in the field of strategy, but debate continues as to its precise nature. This paper contributes to the debate by critically reviewing the development of the RBV to date. The critical appraisal examines the development of the RBV in terms of theory, method, empirical evidence and practical insights. It is contended that the permeable and eclectic nature of the RBV stems from its being a theory about what firms are and how they function, and that its popularity is due to an absence of limiting behavioural assumptions. Finally, the authors provide their own subjective views on where they think RBV scholars should focus their efforts in the future.     

Risks of Paralytic Disease Due to Wild or Vaccine-Derived Poliovirus After Eradication

After the global eradication of wild polioviruses, the risk of paralytic poliomyelitis from polioviruses will still exist and require active management. Possible reintroductions of poliovirus that can spread rapidly in unprotected populations present challenges to policymakers. For example, at least one outbreak will likely occur due to circulation of a neurovirulent vaccine-derived poliovirus after discontinuation of oral poliovirus vaccine and also could possibly result from the escape of poliovirus from a laboratory or vaccine production facility or from an intentional act. In addition, continued vaccination with oral poliovirus vaccines would result in the continued occurrence of vaccine-associated paralytic poliomyelitis. The likelihood and impacts of reintroductions in the form of poliomyelitis outbreaks depend on the policy decisions and on the size and characteristics of the vulnerable population, which change over time. A plan for managing these risks must begin with an attempt to characterize and quantify them as a function of time. This article attempts to comprehensively characterize the risks, synthesize the existing data available for modeling them, and present quantitative risk estimates that can provide a starting point for informing policy decisions.     

A LARGE-SCALE PERSONNEL ASSIGNMENT MODEL FOR THE NAVY*

The U.S. Navy has been trying for years to develop a model to automate its personnel assignment process The requirement of rotating navy personnel frequently between sea duty and shore duty in accordance with multiple policies makes modeling efforts difficult. However, without a model to optimize assignments with regard to multiple policies, navy managers do not know the real impact of personnel assignments. This limits their ability to make effective decisions. This paper summarizes our effort to develop a large-scale network model for the navy's assignment problem. The navy has accepted this model for implementation, replacing the current manual assignment process. The approach in this paper can be generalized to a wide variety of perosnnel assignment problems.