New vaccines have sharply reduced the number of children paralysed by polio and raised hopes that a $5 billion campaign to wipe it out may be close to success, a top public health official said in an interview.

About 404 people worldwide -- mainly young children -- have suffered paralysis from polio since the start of 2007, less than half the 1,017 new cases reported at the same point in 2006, according to the Global Polio Eradication Initiative.

Bruce Aylward, director of the nearly 20-year-old campaign, said new and more effective vaccines had helped combat polio in some of its most stubborn strongholds, including parts of India and Nigeria.

More collaboration between Pakistan and Afghanistan had also helped cut the prevalence of polio in the two other countries where the disease remained endemic, he said.

'It's a pretty exciting time,' the Canadian epidemiologist told Reuters in his office in Geneva.

'I'm kind of afraid to talk about it,' he said with a nervous laugh. 'Everybody is surprised by the degree of progress.'

The incidence of polio has fallen more than 99 per cent since the World Health Organisation, UNICEF, Rotary International and the US-based Centres for Disease Control launched the eradication drive in 1988, when 350,000 people were afflicted each year.

Efforts to eliminate it were thwarted by poor vaccination coverage in pockets of Africa and Asia, which led the virus to re-emerge in dozens of countries previously declared polio-free.

The eradication initiative missed its original 2000 target, and no new goal was set. Aylward said that, in view of advances against the disease, it might be possible to eradicate polio worldwide by the end of 2009.

Children require at least three, and often more, rounds of oral polio vaccine to build up immunity to the disease, which proliferates in areas with poor sanitation.

Immunisation campaigns traditionally used vaccines that combat all of polio's three strains: Type 1 being most virulent, and Type 3 concentrated in more limited areas. Type 2 polio was last found in 1999.

Reflecting a new strategy to focus more aggressively on Type 1 polio -- which spreads faster and causes paralysis more often than Type 3 -- the initiative in 2005 started to shift to new vaccines that fight each single strain with more strength than trivalent models.

Aylward said the deployment of single-strain vaccines 'had really knocked the wind out of Type 1' polio in India's Uttar Pradesh state and in Kano state in northern Nigeria, which had both proved to be been stubborn reservoirs of the virus.

To completely stop the disease, he said India needed to maintain frequent immunisations in areas of rapid population growth, Nigeria must raise the number of children getting vaccine, and security concerns limiting access in Pakistan and Afghanistan must be overcome.

Aylward also cited worries that outbreaks seen this year in the Democratic Republic of Congo, Angola, Somalia, Myanmar and Chad could cause polio to spread further unless those countries and their neighbours keep up regular vaccination campaigns. Reuters