A gift from the twentieth to the twenty-first century

16 World Health • SlstYeor, No. 2, Morch-April 1998 A gilt from the twentieth to the twenty-first century The threat of polio to young lives and limbs will shortly be consigned to history. Photo WHOl).-F Chretien I t all began in a test-tube 50 years ago - the year the World Health Organization began its work. It is a story of international cooperation on a global scale, of a race to develop a vaccine against an incurable dis- ease that has paralysed millions of children, of efforts to broker a cease- fire in the midst of war so that chil- dren on both sides could be immunized, and of record-breaking efforts to immunize hundreds of millions of children on a single day. Its driving force has been a determi- nation to ensure that all children - rich or poor - are protected against polio. The first major breakthrough was in 1948. In the United States, a Harvard Medical School research team, headed by physician John Enders, succeeded in growing poliovirus in cell culture - paving the way for development of a vac- cine against polio. At the time, polio was a little understood and much dreaded disease. In the pre-vaccine era over half a million people were paralysed by polio every year- most of them children under three years old. The turning point came in 1955, when the first polio vaccine - Jonas Salk's inactivated polio vaccine - was licensed for use in the United States. From then on, the number of polio cases began to fall in the indus- trialized countries, where the vaccine was mainly used. But it was another 25-30 years before polio vaccine became widely available to children in developing countries. By then the Salk vaccine had long ago been overtaken by Albert Sabin's live oral polio vaccine, now used in virtually all national immunization programmes. In the 1950s, WHO was quick to recognize the potential of live oral polio vaccines as a global public health tool and played a key role in the development of Sabin's vaccine. Unlike the Salk vaccine, a live atten- uated vaccine could induce not only serum immunity but secretary immu- nity as well. By limiting multiplica- tion of "wild" poliovirus inside the gut, and reducing faecal excretion of the virus, it could provide an effec- tive barrier against circulation of wild polioviruses. With a live vac- cine, it might one day be possible to eradicate the disease. An added advantage was that an oral vaccine would be much easier to administer than the injectable Salk vaccine. From 1952 onwards, WHO steered the development of polio vaccines - establishing international standards to control the manufacture and safety of live attenuated polio- virus vaccines. In 1957 WHO spon- sored the first clinical trials of these vaccines and by 1961 the Sabin vaccine was licensed for use in the World Health • SlstYear, No. 2, March-April 1998 United States. The vaccine (like Salk's) was never patented, and in 1972 Sabin entrusted his seed vac- cines to WHO - together with an exclusive licence to distribute the strains to vaccine manufacturers free of charge, subject to stringent con- trols over the manufacturing process and vaccine safety. His aim was to ensure the continued availability of safe, effective, and affordable polio vaccines for every child - a goal which WHO today pursues for all vaccines through the Global Programme for Vaccines and Immunization and the Children 's Vaccine Initiative. During the 1970s, WHO-spon- sored lameness surveys in develop- ing countries shook the widely held belief that children in the industrial- ized countries carried a larger burden of polio paralysis - revealing that polio was equally widespread among children in developing countries. The need for polio vaccines was universal. In 1974, WHO launched the Expanded Programme on Immunization - one of the major global public health achievements this century. Within two decades, global immunization coverage dur- ing the first year of life against origi- nally six diseases - diphtheria, tetanus, pertussis, measles, tubercu- losis, and polio - soared from 5% to 80% and the number of child deaths was reduced by three million. Buoyed by these achievements, and by the success of efforts to eradi- cate polio in the Americas, the World Health Assembly in 1988 set a global target of polio eradication by the year 2000. In the words of the resolution, it would be "an appropriate gift, together with the eradication of smallpox, from the twentieth to the twenty-first century". WHO launched a polio eradica- tion strategy comprising: high rou- tine immunization coverage with oral polio vaccine; supplementary immu- nization in the form of national immunization days (mass cam- paigns); effective surveillance; and, in the final stages, door-to-door immunization in areas where the virus persists. To carry this out, WHO forged a global alliance in- cluding Rotary International, the United Nations Children's Fund (UNICEF), the US Centers for Disease Control and Prevention (CDC), nongovernmental organiza- tions, donor governments, and min- istries of health in the polio-endemic countries. Over the past decade their support has included not only fund- ing but technical expertise, advocacy, and volunteers. At the outset in 1988, there were about 350 OOO cases of polio world- wide. By 1996 (the latest year for which complete data are available at the time of writing) there were about 40 OOO cases - a reduction of almost 90%. In the Americas, where the last case of polio occurred in 1991 , an international commission certified in 1994 that polio had been eradicated throughout the Western Hemisphere. By the end of 1997, national immunization days had been carried out in almost every country in the world - establishing world records for immunization. During 1996, 400 million children - almost two-thirds of the world 's children under five - were immunized against polio during mass campaigns. In addition, 80% of babies were fully immunized against polio before their first birthday, through routine immunization. In December 1996, and again in January 1997, over 250 million children were immunized against polio during coordinated national immunization days in Asia. In India, which until recently accounted for over half the world's polio cases, 127 Immunization: the universal defence against polio. Photo WHO/H Anenden 17 million children were immunized on a single day in January 1997 - the largest public health event ever organized by a single country. Polio immunization has even been carried out in countries at war. Internationally brokered truces have been negotiated both for routine immunization and mass campaigns - mainly under the aegis of UNICEF - in Afghanistan, El Salvador, Lebanon, the Philippines, Sri Lanka, and Sudan. Elsewhere, unofficial ceasefires have been secured for national immunization days in areas of conflict in Cambodia, India, Iraq, Myanmar, Turkey, and elsewhere. It is too early to say whether polio will be eradicated on target by the year 2000. The countries where polio is still endemic include some of the poorest in the world. In some, health infrastructures have been destroyed by war and neglect, and immunization programmes sus- pended. To make matters worse, many of the almost 60 countries which reported - or failed to report - polio cases during 1996 are still not meeting WHO criteria for adequate surveillance. Elsewhere, donor fatigue and the competing need for funds to combat other infectious diseases - some both more life-threatening and more widespread than polio - pose contin- uing threats. In addition to what governments are spending, an esti- mated US$ 1000 million donor funding is needed up to the year 2005. Without both adequate re- sources and firm political commit- ment to polio eradication in the poorest developing countries, po- liovirus will continue to circulate - both in those countries and beyond. The danger is that, as the number of polio cases continues to fall, people will become complacent - allowing routine immunization coverage to slip and enabling the disease to stage a come-back. It would be a tragedy if the gift of polio eradication turned out to be an empty promise for the children of the 21st century. •