Decision analysis and polio immunization policy

Review of poliovirus modeling performed from 2000 to 2019 to support global polio eradication

INTRODUCTION

Over the last 20 years (2000-2019) the partners of the Global Polio Eradication Initiative (GPEI) invested in the development and application of mathematical models of poliovirus transmission as well as economics, policy, and risk analyses of polio endgame risk management options, including policies related to poliovirus vaccine use during the polio endgame.

AREAS COVERED

This review provides a historical record of the polio studies published by the three modeling groups that primarily performed the bulk of this work. This review also systematically evaluates the polio transmission and health economic modeling papers published in English in peer-reviewed journals from 2000 to 2019, highlights differences in approaches and methods, shows the geographic coverage of the transmission modeling performed, identified common themes, and discusses instances of similar or conflicting insights or recommendations.

EXPERT OPINION

Polio modeling performed during the last 20 years substantially impacted polio vaccine choices, immunization policies, and the polio eradication pathway. As the polio endgame continues, national preferences for polio vaccine formulations and immunization strategies will likely continue to change. Future modeling will likely provide important insights about their cost-effectiveness and their relative benefits with respect to controlling polio and potentially achieving and maintaining eradication.

Poliovirus vaccines. Progress toward global poliomyelitis eradication and changing routine immunization recommendations in the United States

Poliomyelitis prevention in the United States has relied virtually exclusively on OPV during the past 30 years. Starting in 1997, a major change in the poliomyelitis vaccination policy occurred, facilitated by substantial progress toward worldwide poliomyelitis eradication. A sequential schedule of IPV followed by OPV became the preferred means to prevent poliomyelitis, although an all-OPV and an all-IPV schedule were considered acceptable alternatives. In 1999, two doses of IPV were recommended to start the primary series, followed by two doses of either poliovirus vaccine. As of January 2000, an all-IPV schedule is currently being implemented in the United States for routine childhood vaccination. Several unusual features are associated with the major public health policy change from an all-OPV to a sequential schedule, including (1) the process of involving a neutral party (i.e., the IOM); (2) the perceived concerns expressed before the change in policy with regard to provider and parent compliance, which could affect the hard-earned gains in raising immunization coverage rates; (3) the ethical issues surrounding the change (e.g., societal versus individual protection) and the influence that a single case of VAPP may have on national policy; (4) the relative lack of importance of cost-effectiveness data; and (5) the weight of progress in the global polio eradication initiative spurring the change in the United States and, increasingly, in other industrialized countries. The IOM assisted in the evaluation of the national poliomyelitis vaccination policy in 1977 and again in 1988. The 1988 review recommended that a sequential IPV-OPV schedule be considered at such time that a combination vaccine becomes available. Also, the IOM raised several important questions. Extensive research to address the questions raised by the IOM had been conducted so that, in 1996, more data were available for the decision-making process. The primary reasons for the change in vaccination policy were (1) the continued occurrence of VAPP in the absence of indigenously acquired wildtype poliovirus-associated paralytic disease, (2) the reduced risk for importation and spread of wild-type poliovirus caused by the progress of the global polio eradication initiative, (3) evidence from vaccine trials that combined IPV-OPV schedules are safe and immunogenic, and (4) maintenance of high levels of population immunity to poliovirus. The global effect of a national change in poliomyelitis vaccination policy was also considered in this policy-making process. Some members of the public health and medical communities raised objections that an increased reliance on IPV in the United States could lead other countries, especially developing countries, to inappropriately abandon OPV and increase reliance on IPV for routine vaccination. Experience from the global smallpox eradication campaign indicated that this scenario was unlikely. The United States ceased vaccinating against smallpox in 1971, 6 years before smallpox was eliminated from the world, without jeopardizing the global smallpox campaign. Subsequently, the effect on the global eradication initiative has been negligible. This article illustrates the potential discrepancy between expressed theoretic concerns about the number of injections and the actual practice once vaccination policy recommendations become the standard of care and that appropriate training and education can overcome these initial concerns. The authors found that compliance with the recommended use of IPV for the first and second doses as part of the sequential schedule was high, independent of socioeconomic status and ethnicity. The need for additional injections did not present a barrier to completion of the recommended childhood immunization schedule. (ABSTRACT TRUNCATED)

Using explicit decision rules to manage issues of justice, risk, and ethics in decision analysis: when is it not rational to maximize expected utility?

Concepts of justice, risk, and ethics can be merged with decision analysis by requiring the analyst to specify explicity a decision rule or sequence of rules. Decision rules are categorized by whether they consider: 1) aspects of outcome distributions beyond central tendencies; 2) probabilities as well as utilities of outcomes; and 3) means as well as ends. This formulation suggests that distribution-based decision rules could address both risk (for an individual) and justice (for the population). Rational choice under risk if choices are one-time only (vs. repeated events) or if one branch contains unlikely but disastrous outcomes might ignore probability information. Incorporating risk attitude into decision rules rather than utilities could facilitate use of multiattribute approaches to measuring outcomes. Certain ethical concerns could be addressed by prior specification of rules for allowing particular branches. Examples, including selection of polio vaccine strategies, are discussed, and theoretical and practical implications of a decision rule approach noted.

A ten-year experience in control of poliomyelitis through a combination of live and killed vaccines in two developing areas

We describe a successful program of poliomyelitis control using a combination of killed and live polio vaccines over a 10-year period in two developing areas, the West Bank and Gaza, adjacent to a relatively developed country, Israel. During the 1970s, immunization using live trivalent oral polio vaccine (OPV) in these areas covered more than 90 percent of the infant population. Nevertheless, the incidence of paralytic polio continued to be high, with many cases occurring in fully or partially immunized persons. It was thought that this could be due to interference with OPV take by other enteroviruses present in the environment due to poor sanitary conditions in these areas. A new policy combining five doses of OPV with two doses of inactivated polio vaccine (IPV) was adopted and implemented in 1978. In the 10 years since then, immunization coverage of infants increased to an estimated 95 percent and paralytic poliomyelitis has been controlled, despite exposure to wild poliovirus from neighboring countries including an outbreak in Israel in 1988. This experience suggests that wide coverage using the combination of IPV and OPV is an effective vaccination policy that may make eradication of polio possible even in developing areas.