A new vaccine against the leading cause of childhood diarrhoea could save thousands of lives worldwide.

The new drug has been found to be almost 90% effective in preventing the intestinal infection rotavirus.

Rotavirus kills up to 600,000 children every year in developing countries.

The dehydration it causes puts millions of children into hospital and costs the US over $1bn a year to treat.

The 89-12 vaccine, developed at The Children's Hospital Research Foundation in Ohio, is the only rotavirus vaccine in development which contains a weakened form of the human virus.

Dr Richard Ward, one of the US doctors behind the vaccine which was developed at The Children's Hospital Research Foundation in Ohio, told Reuters: "It's a human retrovirus and we're protecting against a human rotavirus.

"The other vaccines are all animal strains that are trying to protect against humans. Their ability to elicit a proper immune response may not be as good as it would be if it were a human strain."

Writing in The Lancet, Dr Ward and his colleagues say phase II clinical trials on the vaccine, licensed to SmithKline Beecham by developers Avant Immunotherapeutics Inc., have proved very effective.

The doctors tested the vaccine on 215 infants.

Half were given the vaccine and half received a placebo.

Eighteen children developed diarrhoea and vomiting, but only two were in the vaccine group.

The only side effects of the vaccine noted were a mild fever.

However, although use of a human strain could produce better protection, the researchers say there is also a danger that it could mean children develop rotavirus.

They say larger trials and trials in developing countries are needed before the vaccine can be licensed.

First vaccine

Last year, the US granted a licence to the first rotavirus vaccine, RotaShield, although there were concerns about its cost to developing countries.

The 89-12 vaccine would be cheaper since it is developed from only one strain.

RotaShield has also run into further problems.

Some children who have taken it have developed bowel problems and US federal health officials have called for it to be suspended.

Wyeth-Ayerst Laboratories, which developed the vaccine, want it to be withdrawn until November so that researchers can investigate if there is a link with bowel problems.

Rotavirus is estimated to infect approximately 75% of all children before the age of five years. One in 40 children is hospitalised, but good health care, especially replacing lost fluids, limits deaths.