Chapter 4: Polio Eradication: the final challenge
Prospects for a polio-free future
As the result of an aggressive, deliberate and internationally coordinated effort, polio has changed from being a devastating disease with a global distribution to one that is now geographically restricted to seven countries. To capitalize on this progress, substantial effort is now required to interrupt the final chains of polio transmission, certify that achievement, and minimize the risk of polio being reintroduced in the future. The polio partner- ship's Polio Eradication Strategic Plan 2004--2008 summarizes these challenges in its major objectives.
First, the final chains of poliovirus transmission must be interrupted in the remaining seven countries. Particular effort will be required in India, Nigeria and Pakistan, which now account for 99% of the world's polio burden and remain a source of importation to polio-free areas. Within these countries, five of the 76 states or provinces are the key to global eradication; with sustained high-level political engagement, oversight and accountability in each one, high-quality NIDs could rapidly reach all children and halt polio transmission within 12 months.
Second, the global interruption of wild poliovirus transmission must be verified by the Global Commission for the Certification of Poliomyelitis Eradication. Certification requires that all countries provide documentation demonstrating the absence of wild poliovirus circulation for at least three years, in the presence of high-quality surveillance, as well as the "containment" of all stocks of wild poliovirus. Containment requires that within one year of the interruption of wild poliovirus transmission globally, countries will have identified all stocks of wild poliovirus and ensured their storage and handling under appropriate biosafety conditions (see Figure 4.3).
Third, appropriate policies will need to be developed, and internationally agreed, for the post-certification era. These policies must be designed to both minimize the risk of reintroduction of wild poliovirus and ensure the global capacity to manage such an event should it occur. Consequently, policies will be needed in four areas: polio detection and notification, long-term biocontainment of all poliovirus strains (that is, wild and vaccine strains), polio vaccine stockpiles, and routine immunization (11). The development of these policies will be even more complex than it was for smallpox, for a number of reasons. For example, the very low risk of vaccine-derived polioviruses regaining the capacity to cause outbreaks is now well documented. Furthermore, the risks of international terrorism have substantially affected the willingness of some policy-makers to plan for the discontinuation of routine polio immunization in the near future, regardless of the economic benefits. Because of the complexity of these issues, ongoing research in this area will be complemented by broad consultation with governments and stakeholders through the World Health Assembly and other forums from 2004 onwards (11).