Polio eradication: the beginning of the end

Abstract

Since the Global Polio Eradication Initiative was launched in 1988, the number of polio cases worldwide has dropped from an estimated 350 000 that year to under 1000 in 2003. Now, many areas of the world have been certified free of the disease—the Americas in 1994, the western Pacific in 2000, and Europe in 2002. Polio remains endemic in only six countries: Pakistan, India, Egypt, Afghanistan, Niger, and Nigeria. Although the initial target date set for global eradication was 2000, the achievements of the campaign are staggering: in 2002 alone, 500 million children under the age of 5 years were vaccinated in 93 countries.Eradication of polio in the remaining hotspots is tantalisingly close: four of the six remaining endemic countries—India, Pakistan, Afghanistan, and Egypt— are on the brink of success. The campaign in these countries will now focus on “mopping up” the virus by initiating massive immunisation campaigns in response to each new case. In January, representatives from these countries signed up to a final push, pledging to interrupt transmission of the disease by the end of the 2004. With numbers of cases in these countries in the tens rather than the hundreds, the end is in sight.But ultimately the success of the whole campaign— which has so far cost an estimated US$3 billion—now hinges on west and central Africa. The campaign hit substantial setbacks last August when religious leaders in several northern states of Nigeria raised doubts about the safety of the vaccine, claiming that it was contaminated with oestrogen, progesterone, and even HIV. Immunisation dropped to below 20% in some areas and as a consequence, 145 of the 201 cases reported so far this year have been in Nigeria. However, it is perhaps more worrying that cases have also now been reported in neighbouring countries that had previously been polio free—such as Cote d'Ivoire, Burkina Faso, and the Central African Republic—as well as some previously polio-free areas of Nigeria, including the densely populated city of Lagos.Although vaccination has yet to resume in Nigeria, unofficial reports (see page 388 of this issue) claim that the safety concerns have been resolved by the importation of vaccine from a verified Indonesian source and that “catch-up” vaccination programmes will be initiated, with the support of WHO, in July and August before the high transmission season in September and October. On May 17, WHO announced that it will launch large-scale immunisation campaigns in 21 African countries in an attempt to finally rid the continent of the virus by early 2005.With the polio alliance—WHO, UNICEF, Rotary International and the US Center for Disease Control— quietly confident of meeting their 2005 target, it is now time to look to the future. In a new Global Polio Eradication Strategic plan announced in January, WHO outlined its policy for 2004–2008. A 3 year certification period, during which high-quality surveillance and vaccination with the oral polio vaccine will continue, is required before the world can be declared polio free. After this period, use of the oral polio vaccine will be stopped because the use of a live vaccine carries a risk, albeit a very small one, of a vaccine-derived outbreak, such as that reported on Hispaniola in 2002.Use of the oral polio vaccine has already been phased out in many developed countries, which now offer vaccination with an injectable alternative that does not contain the live virus and therefore carries no risk of re-emergence. But in developing countries, the cost of an injectable vaccine is too high and the practical implications too vast. With WHO planning to phase out oral polio vaccine after certification, governments will be faced with the choice of continuing to vaccinate but with the injectable vaccine, finding an alternative vaccination strategy, or stopping vaccination altogether. WHO's current policy is to support governments in making these important decisions on a country by country basis, but clearly a global consensus needs to be reached to maintain a polio-free world. Otherwise, vaccination in developing countries is likely to cease altogether, creating an unacceptable discrepancy between rich and poor.The certification period will be critical for the whole campaign. A tough job lies ahead for the alliance: with a funding gap of US$ 150 million to bridge for 2004–2005, keeping donors interested beyond eradication is a major challenge. The temptation to take the foot off the pedal will be strong once a year has gone by with no reports of new cases. But maintaining high-quality surveillance programmes through the 3 year period, or even longer, is essential. Certification is just the beginning of the end: polio's greatest ally now is complacency. It would be disastrous if, after all this time, money, and effort, the largest public-health campaign ever was to fall at the final hurdle. Since the Global Polio Eradication Initiative was launched in 1988, the number of polio cases worldwide has dropped from an estimated 350 000 that year to under 1000 in 2003. Now, many areas of the world have been certified free of the disease—the Americas in 1994, the western Pacific in 2000, and Europe in 2002. Polio remains endemic in only six countries: Pakistan, India, Egypt, Afghanistan, Niger, and Nigeria. Although the initial target date set for global eradication was 2000, the achievements of the campaign are staggering: in 2002 alone, 500 million children under the age of 5 years were vaccinated in 93 countries. Eradication of polio in the remaining hotspots is tantalisingly close: four of the six remaining endemic countries—India, Pakistan, Afghanistan, and Egypt— are on the brink of success. The campaign in these countries will now focus on “mopping up” the virus by initiating massive immunisation campaigns in response to each new case. In January, representatives from these countries signed up to a final push, pledging to interrupt transmission of the disease by the end of the 2004. With numbers of cases in these countries in the tens rather than the hundreds, the end is in sight. But ultimately the success of the whole campaign— which has so far cost an estimated US$3 billion—now hinges on west and central Africa. The campaign hit substantial setbacks last August when religious leaders in several northern states of Nigeria raised doubts about the safety of the vaccine, claiming that it was contaminated with oestrogen, progesterone, and even HIV. Immunisation dropped to below 20% in some areas and as a consequence, 145 of the 201 cases reported so far this year have been in Nigeria. However, it is perhaps more worrying that cases have also now been reported in neighbouring countries that had previously been polio free—such as Cote d'Ivoire, Burkina Faso, and the Central African Republic—as well as some previously polio-free areas of Nigeria, including the densely populated city of Lagos. Although vaccination has yet to resume in Nigeria, unofficial reports (see page 388 of this issue) claim that the safety concerns have been resolved by the importation of vaccine from a verified Indonesian source and that “catch-up” vaccination programmes will be initiated, with the support of WHO, in July and August before the high transmission season in September and October. On May 17, WHO announced that it will launch large-scale immunisation campaigns in 21 African countries in an attempt to finally rid the continent of the virus by early 2005. With the polio alliance—WHO, UNICEF, Rotary International and the US Center for Disease Control— quietly confident of meeting their 2005 target, it is now time to look to the future. In a new Global Polio Eradication Strategic plan announced in January, WHO outlined its policy for 2004–2008. A 3 year certification period, during which high-quality surveillance and vaccination with the oral polio vaccine will continue, is required before the world can be declared polio free. After this period, use of the oral polio vaccine will be stopped because the use of a live vaccine carries a risk, albeit a very small one, of a vaccine-derived outbreak, such as that reported on Hispaniola in 2002. Use of the oral polio vaccine has already been phased out in many developed countries, which now offer vaccination with an injectable alternative that does not contain the live virus and therefore carries no risk of re-emergence. But in developing countries, the cost of an injectable vaccine is too high and the practical implications too vast. With WHO planning to phase out oral polio vaccine after certification, governments will be faced with the choice of continuing to vaccinate but with the injectable vaccine, finding an alternative vaccination strategy, or stopping vaccination altogether. WHO's current policy is to support governments in making these important decisions on a country by country basis, but clearly a global consensus needs to be reached to maintain a polio-free world. Otherwise, vaccination in developing countries is likely to cease altogether, creating an unacceptable discrepancy between rich and poor. The certification period will be critical for the whole campaign. A tough job lies ahead for the alliance: with a funding gap of US$ 150 million to bridge for 2004–2005, keeping donors interested beyond eradication is a major challenge. The temptation to take the foot off the pedal will be strong once a year has gone by with no reports of new cases. But maintaining high-quality surveillance programmes through the 3 year period, or even longer, is essential. Certification is just the beginning of the end: polio's greatest ally now is complacency. It would be disastrous if, after all this time, money, and effort, the largest public-health campaign ever was to fall at the final hurdle.