IN 1988 the World Health Assembly decided to eradicate the poliomyelitis virus worldwide by the year 2000. The director general of the World Health Organisation, Dr Hiroshi Nakajima described the plan as 'a fitting gift from the health workers of this century to the children of the next'. At the time, the number of polio cases recorded for the year was 35,255. The project is now at the halfway mark, and this year's World Health Day, today, has been dedicated to reviewing the achievements and further promoting the cause. And it is working, especially in China. Statistics provided by the World Health Organisation show that last year, the total number of polio cases reported worldwide was reduced to 6,241 in 1994. Large areas of the world have been declared polio-free, and it is believed 145 countries have now effectively eradicated polio from within their borders. Hong Kong's last recorded case of the disease was in 1985. China has been declared a world leader in the fight and Dr Nakajima will spend World Health Day in Beijing, talking with medical authorities to highlight their astounding success. Mass immunisation campaigns have been the trend around the world for some time, but China, having two years ago set itself the goal of eradicating polio by 1995, has established itself as the expert in this area. National Mass immunisation days held in December 1993 and January 1994 saw 82 million and 83 million children respectively vaccinated over periods of just two days each. Despite outbreaks of about 5,000 cases in 1989 and 1990, polio is visibly on the retreat in China, with only 653 cases reported in 1993. Virological surveys show that it was present in seven of 30 provinces in 1993, but six months later was found in just one. 'We are trying to use China as an example of the successful programme that can be achieved in just one or two years,' Dr Nakajima said. 'This will give the example to the southern nations which will help achieve our goal of complete eradication by the year 2000.' Today about 15 countries in Europe and the eastern Mediterranean will provide polio vaccine to their children simultaneously. Last year the region of the Americas, including both the North and South American continents, was declared polio-free. Having set themselves the goal of eradicating polio from the western hemisphere by 1990, national governments joined with international health organisations to promote vaccinations and general education on symptoms and possible means of transmission. In 1985, nearly 1,000 cases were reported in the American region, down from 10,000 cases a year in the mid-70s. Cuba was the first to introduce large-scale immunisation programmes in 1962, and other countries quickly followed suit. By the end of 1990 only 18 cases were reported in the region. In 1991, the figure had dropped to nine cases reported - eight in Columbia and one in Peru. The case in Peru - that of a two-year-old boy called Luis Fermin Tenorio Cortez - prompted the immunisation of two million children in a single week. Now aged five, Luis still walks with a limp, although he has been known to kick a soccer ball around enthusiastically. His is believed to be the last polio case in the Americas, and by September 29, 1994, the disease had been declared effectively eradicated. When the Expanded Programme on Immunisation (EPI) was established in 1974, fewer than five per cent of the world's children born each year were immunised. Since then, immunisation programmes have been established in every country. In 1993 it was estimated that 75 per cent of those born that year were fully immunised. The WHO estimates that at current levels of immunisation, EPI prevents an estimated 2.9 million deaths from measles, neo-natal tetanus and whooping cough and 560,000 cases of polio each year. It believes the western Pacific region is about to become the second region which can be declared officially polio-free. However, Dr Nakajima said there were still substantial problems in South Asia, in countries such as Bangladesh and Pakistan, which continue to record upward of 2,000 polio cases a year. 'The main problem is still southern Asia and West Africa,' he said. 'They are progressing quite well but we hope to show them that if China can reach its goals within two or three years, they can also achieve eradication programmes.' Dr Nakajima said the key to the success of the plan was the introduction of national immunisation days, which provide simultaneous vaccines to all children under five and detailed systems of surveillance so that any sign of paralysis in children can be quickly identified. 'As fewer and fewer cases occur, widespread house-to-house immunisation finally reduces transmission to zero, thus leading to eradication,' he said. But to complete the goal, he said it was essential that health services joined forces with governments and non-government organisations, and the public generally. The WHO director of the Global Programme for Vaccines and Immunisation, Dr Jong-wook Lee told World Health magazine that in order to convince the world of the urgent need for immunisation, a change in philosophy was required. 'There is a need to change the philosophy from a simplistic approach - all children have a right to be immunised - to a broader one which is that all children must be protected from death and disability by making the best vaccines available and using them in the most effective manner,' Dr Lee said. The battle against polio is greatly helped by the development of vaccines, allowing children to be immunised against the spread of the disease. The WHO estimates about 80 per cent of the world's children now have access to safe vaccines. However immunisation coverage is now falling - there are at least 18 countries where immunisation coverage is below 50 per cent. Even with these impressive achievements, the WHO estimates that 110,000 children are still being crippled by polio each year. These days, the international cost of immunisation programmes runs at more than US$800 million (about HK$6.2 billion), nearly two-thirds of which is spent on the vaccine itself. That will be money well spent if the ultimate goal can be achieved - a millennium in which the polio virus does not exist.