By Abigail Hauslohner

KHARTOUM, Aug 8 (Reuters) - Sudan has vaccinated 4.9 million children in the north after reports of polio cases in neighbouring Chad triggered fear of transmission across the border, a U.N. official said on Wednesday.

The U.N. children's agency (UNIECF) and the World Health Organisation (WHO) funded and trained some 40,000 personnel to vaccinate children under the age of five, Edward Cawardine, a senior UNICEF official said.

"What's unique is it's an additional campaign that we've put together with the ministry of health because of the reports of some cases in Chad," Cawardine told Reuters, adding it was a swift three-day campaign.

Sudan's Darfur region, hit by a four-year-old revolt, borders Chad. Heavy rains and floods throughout the country have also raised fears that epidemics could spread.

There have not been any reported cases of polio in Sudan since 2005 but UNICEF and WHO carry out regular mass vaccination campaigns in the country, Cawardine added.

Polio, which is typically spread from contact with faeces, is incurable and can lead to irreversible paralysis. Death occurs in about 5-10 percent of paralysed patients when their breathing muscles are immobilised.

The flooding, which has affected some 500,000 people and killed 64, may have prevented the immunisation campaign from reaching up to 20 percent of the children targeted, Cawardine said. The campaign will return to those areas when the flooding subsides, he added.

Cawardine said the campaign was also unable to reach the region of Adila in South Darfur due to heavy fighting.

The WHO says its Global Polio Eradication Initiative, launched in 1988, has reduced the number of polio cases worldwide from 350,000 in 125 endemic countries in 1951 to 337 reported cases so far in 2007.

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