Global lessons from India’s poliomyelitis elimination campaign

Abstract

In its history of more than two decades, the Global Polio Eradication Initiative (GPEI), led by national governments and the World Health Organization, has made remarkable headway, punctuated by a few public health riddles. Globally, the number of cases of poliomyelitis (polio) confirmed annually dropped from an estimated 350 000 in 1988 to 1651 in 2008. (1) By 2 December 2009, the number of cases of wild poliovirus (WPV) infection reported by endemic countries had declined somewhat, but the number reported by non-endemic countries had nearly tripled (Fig. 1). Indigenous WPV type 1 (WPV1) and WPV type 3 (WPV3) have been eliminated from all countries except Afghanistan, India, Nigeria and Pakistan, yet in 2008 outbreaks resulting from imported cases were reported by 12 countries, in five of which transmission has lasted for more than 12 months. Furthermore, cases of infection with the vaccine-derived poliovirus still occur, and this virus will continue to circulate and cause outbreaks for as long as oral polio vaccine is used. The time has not yet come when routine vaccination is no longer required, a hallmark that eradication has been achieved. In the midst of these virological considerations, the key lesson that emanates from the Indian experience is that the social determinants of programme implementation are as important as the technical ones--and this lesson has a significant bearing on other disease elimination programmes as well. Polio elimination in India Efforts to eliminate polio in India may provide insights as to the factors that can influence the success or failure of polio elimination strategies and ultimate disease eradication. In India, 659 cases of WPV infection (predominantly with WPV3) and 15 cases of vaccine-derived poliovirus infection had been reported by 4 December 2009, about 80% of them in the state of Uttar Pradesh and 17% in the state of Bihar. Children aged less than 2 years were the most affected group. On the surveillance front, stool collection within 14 days of the onset of paralysis, as mandated by India's National Polio Surveillance Project, has hovered between 84% and 85% of all reported cases of acute flaccid paralysis in 2008 and 2009--figures that maintain the prescribed target of 80% or above. This is a critical component of the polio eradication strategy, since ascertaining that the poliovirus is the cause of a child's paralysis is only possible by examining a stool specimen. However, in the last decade the incidence of nonpolio acute flaccid paralysis in India has increased 10-fold (from the WHO benchmark of at least 1 per 100 000), and in 2009 Bihar reported 29 cases per 100 000 population (based on stool tests conducted in 86% of cases of acute flaccid paralysis). Questions have thus been raised about the robustness of polio surveillance, and there is concern that cases of poliomyelitic acute flaccid paralysis that are reported late may be lurking among suspected cases. Under the GPEI Strategic Plan 2009-2013, the goal is to achieve polio eradication by 2013. With only 66 cases of WPV infection in 2005, India was seemingly at the threshold of eradicating polio; however, the 10-fold rise in cases of infection by WPV observed over the four ensuing years has put the goal beyond reach. There is a need to critically re-examine realities on the ground in India in an effort to understand what has gone wrong. Supplementary immunization activities The current polio elimination strategy has focused primarily on interrupting WPV1 transmission based on the epidemiological argument that WPV1 causes higher rates of paralysis than other wild poliovirus types and is likely to spread to polio-free areas. In 2005, monovalent oral polio vaccine against WPV1 (mOPV1) replaced the trivalent oral polio vaccine (tOPV) in some supplementary immunization rounds. After the WPV1 outbreak in 2006, the mOPV1 was administered to children through several supplementary immunization activities (SIAs). …