Reaching the last one per cent: progress and challenges in global polio eradication

Since its launch in 1988, the World Health Organization's Global Polio Eradication Initiative has reduced worldwide polio incidence by >99%. The most dramatic progress was achieved up to the year 2000, the original eradication target date, but subsequent years have seen only limited progress in preventing the last 1% of cases. Recent gains in India and Nigeria have been offset by continued endemicity in Pakistan and Afghanistan, and repeated reseeding of wild poliovirus into polio-free areas has led to large outbreaks and re-established transmission. Although wild poliovirus type 2 was eradicated in 1999 and wild poliovirus type 3 may be nearing eradication, the continued emergence of circulating vaccine-derived polioviruses, especially type 2, presents ongoing challenges to stopping all poliovirus transmission.

► The Global Polio Eradication Initiative (GPEI) reduced global polio incidence by >99%. ► After rapid progress from 1988 to 2000, the GPEI stalled over the past decade. ► The last indigenous wild poliovirus (WPV) case in India was in January 2011. ► Eradication in India, once the most intense WPV reservoir, re-energized the GPEI. ► Use of bivalent (1 + 3) oral poliovaccine sharply reduced WPV type 3 (WPV3) circulation. ► Imported WPV caused recent large outbreaks in several countries in Africa and Asia. ► Immunity gaps increase WPV and circulating vaccine-derived poliovirus (cVDPV) risk. ► cVDPVs, particularly type 2, have caused outbreaks in 18 countries since 2000. ► The GPEI has addressed challenges far more daunting than envisioned in 1988.