The global polio eradication initiative: lessons learned and prospects for success.

Following the rapid progress towards interrupting indigenous wild poliovirus transmission in the Americas in the early 1980s, the Global Polio Eradication Initiative (GPEI) was launched with a resolution of the World Health Assembly (WHA) in 1988. The GPEI built on many lessons learned from smallpox eradication, including the large-scale deployment of technical assistance, implementing agendas of innovation and research and the use of professionally planned and guided advocacy. By the year 2000, the incidence of polio globally had decreased by 99% compared with the estimated >350,000 cases reported from 125 endemic countries in 1988. By 2002, three WHO Regions (the Americas, Western Pacific and European Regions) had been certified polio-free. By 2005, transmission of indigenous wild poliovirus (WPV) had been interrupted in all but 4 'endemic' countries: India, Nigeria, Pakistan and Afghanistan, where eradication efforts effectively stalled. WPV exported from northern Nigeria and northern India subsequently caused >50 outbreaks and paralysed >1500 children in previously polio-free countries across Asia and Africa. In each of the four remaining polio-endemic countries different challenges, or a combination of factors, prevented to build up sufficient levels of population immunity to stop transmission. Consequently, specific strategies were increasingly tailored to each setting. A new 2010-2012 GPEI Strategic Plan was developed which brought together several approaches to overcome the remaining hurdles to eradication, including the large-scale use of bivalent oral poliovaccine (bOPV) in supplementary immunization activities (SIAs). By the end of 2010, the impact of the new GPEI Strategic Plan 2010-2012 was apparent. Compared to 2009, the number of new polio cases in 2010 fell by 95% in both northern Nigeria and northern India, the world's largest remaining reservoirs of indigenous WPVs. By mid-2011, India had not reported a polio case for more than 5 months, and in Nigeria, endemic transmission appeared to be restricted to the north-east and north-west corners of the country. While polio cases due to WPV type 3 were still being detected in west and central Africa, the overall level of WPV3 transmission globally was at an all-time low. Uncontrolled WPV transmission appeared to be restricted to Chad and Pakistan, which increasingly represented the greatest risks to the GPEI. Although insufficient financing continued to be a major concern, political support for completing polio eradication in polio-infected countries was stronger than ever by mid-2011. While continued transmission in some areas, particularly in Pakistan and Chad, still had to be controlled as a matter of urgency, there were real opportunities to achieve new landmarks in polio eradication, especially in the key WPV reservoirs of India and Nigeria, setting the stage for polio to soon follow smallpox into the history books.