R. Bruce Aylward

Inherent in the decision to launch the Global Polio Eradication Initiative in 1988 was the expectation for many people that immunization against poliomyelitis would eventually simply stop, as had been the case with smallpox following its eradication in 1977. However, the strategies for managing the risks associated with a "polio-free" world must be continuously refined to reflect new developments, particularly in our understanding of the live polioviruses in the oral poliovirus vaccine (OPV) and in the international approach to managing potential biohazards. The most important of these developments has been the confirmation in 2000 that vaccine-derived polioviruses (VDPVs) can circulate and cause polio outbreaks, making the use of OPV after interruption of wild poliovirus transmission incompatible with a polio-free world. A comprehensive strategy has been developed to minimize the risks associated with eventual OPV cessation, centered on appropriate long-term biocontainment of poliovirus stocks (whether for vaccine production, diagnosis, or research), the controlled reintroduction of any live poliovirus vaccine (i.e., from an OPV stockpile), and appropriate use of the inactivated poliovirus vaccine (IPV). Although some aspects of this risk management strategy are still debated, there is wide agreement that no strategy would entirely eliminate the potential risks to a polio-free world. The current strategy for risk management in a polio-free world will continue to evolve with better characterization of these risks and the development of more effective approaches both to reduce those risks and to limit their consequences should they occur.

Since its launch in 1988, the Global Polio Eradication Initiative has grown into one of the largest international health efforts in history, operating in every country and area in the world. The burden of polio disease has been reduced by over 99%, and the number of countries with indigenous virus has fallen from more than 125 to just four. As importantly, a strong surveillance and laboratory infrastructure has been established for vaccine-preventable diseases (including measles, tetanus, yellow fever, rubella and Japanese encephalitis), and a massive investment has been made in the physical infrastructure and human resources needed to deliver routine immunizations and other health services in developing countries. Between 2000 and 2003, new challenges to polio eradication emerged, threatening the interruption of the transmission of wild poliovirus globally and the eventual elimination of any residual polio disease as the result of the continued use of oral polio vaccines. By the end of 2005, a range of solutions had been developed to address these late challenges, including two new monovalent oral polio vaccines, new and robust international standards for the response to polio outbreaks, and renewed political commitment across the countries that remain infected. As importantly, a comprehensive strategy had been established for managing the long-term risks of paralytic polio, centred, ironically, on the eventual elimination from routine immunizations of the vaccine that is still central to the success of the global eradication effort.

Introduction The allure of eliminating diseases forever through eradicating their causative organisms no doubt tantalised physicians and politicians even before germ theory changed the course of medicine and public health profoundly in the 19th century. Only when William Crawford Gorgas, a major general in the US army and a surgeon, embarked on the ill fated quest to eradicate yellow fever from the jungles of Panama in 1915,1 however, did someone actually try to test the theory. Although Major General Gorgas had to abandon the dream of a world rid of yellow fever, he did leave behind concepts that continue to underpin the practice, and politics, of eradication today.2

The 20-year, U.S. $4 billion-dollar international effort to eradicate wild polioviruses now includes monovalent oral poliovirus type 1 vaccine (mOPV1), which was first given to 40 million children in India in April 2005. As this vaccine is being introduced to eliminate some of the last poliovirus reservoirs, the Global Polio Eradication Initiative is planning for the eventual synchronized worldwide cessation of the routine use of all oral poliovirus vaccines (OPVs) because of their capacity to cause, rarely, outbreaks of paralytic poliomyelitis. This Policy Forum reviews the feasibility and implications of eventually stopping the use of live polio vaccines.

Twenty-five years after the eradication of smallpox, the ongoing effort to eradicate poliomyelitis has grown into the largest international health initiative ever undertaken. By 2004, however, the polio eradication effort was threatened by a challenge regularly faced by public health policymakers everywhere—misperception about the benefits and risks of vaccines. The propagation of false rumors about oral poliovirus vaccine safety led to the reinfection of 13 previously polio-free countries and the largest polio epidemic in Africa in recent years. With deft management of such challenges by local, national, and international health authorities, poliomyelitis, a disease that threatened children everywhere just 2 generations ago, could soon be relegated to history like smallpox before it.

Between 1988 and 2004, the Global Polio Eradication Initiative grew to become the largest international health effort in history, operating in every country of the world. An estimated 10 million health workers and volunteers have been engaged in implementing the necessary polio supplementary immunization activities (SIAs) on a recurring basis, and at least 35,000 well-trained workers have been conducting polio surveillance. A combination of task simplification, technological innovations and adaptation of strategies to fit local circumstances has allowed the Initiative to use a wide range of workers and volunteers, from both inside and outside the health sector, to deliver the polio vaccine during SIAs and to monitor progress in virtually every area of every country, regardless of the health infrastructure, conflict, geography and/or culture. This approach has required sustained political advocacy and mass community mobilization, together with strong management and supervisory processes. Non-monetary incentives, reimbursement of costs and substantial technical assistance have been essential. Given the unique features of eradication programmes in general, and polio eradication in particular, the implications of this approach for the broader health system must continue to be studied if it is to be replicated for the delivery and monitoring of other interventions.