By Ania Lichtarowicz
BBC health reporter
A nationwide polio vaccination campaign has started in India as part of a World Health Organization initiative to eradicate the virus around the world.
The authorities hope the disease will be eradicated
More than 170 million Indian children under the age of five are being immunised over the next three days.
Despite an epidemic in 2002, India - by vaccinating as many children as possible with multiple doses - looks likely to stop the spread next year.
Another 80 million children are being vaccinated in 24 African countries.
Future in doubt
In the last campaign, about 90% of children were immunised and this time health care workers will be trying to reach those in remote areas.
There is concern though about polio in the Ivory Coast - this year 15 children have been paralysed by the virus, and conflict there means that vaccinations have been postponed.
Further campaigns in Egypt, Afghanistan and Pakistan - the remaining polio endemic countries - are planned for later this year.
But future campaigns in the UN's Global Polio Eradication Initiative are in doubt.
An additional $200m is needed to continue vaccinations in 2005 and without this money the virus will be able to spread quickly in unimmunised children throughout the world.