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A live oral cholera vaccine was found to be safe among Bangladeshi children, raising hopes that it might one day be used to combat outbreaks of the disease.

The research team that carried out the trials of the vaccine, called Peru-15, says that a single-dose vaccine that is easy to administer to infants is badly needed in developing countries.

Cholera causes severe diarrhoea and if left untreated can lead to severe dehydration and death. It kills tens of thousands of people worldwide every year — mostly in developing countries — due to poor water infrastructure.

The trials led by David Sack of the International Centre for Diarrhoeal Diseases Research in Dhaka, Bangladesh involved 240 children aged between 9 months and 5 years.

The team tested two strengths of the vaccine prepared from a weakened and genetically engineered form of the El Tor Inaba strain of cholera that is currently circulating in South Asia.

Children were given either a strong vaccine dose, a weak dose, or a placebo.

The vaccinated children showed no adverse effects. Immune responses were stronger for those given the higher strength vaccine; these participants produced four times as many immune cells as those given a placebo.

"The results to date are very encouraging and show that this vaccine is worthy of further testing for efficacy in a country that is endemic for cholera," James Kaper, professor at the US-based University of Maryland's Center for Vaccine Development, told SciDev.Net.

Gautam Chatterjee of Kolkata Medical College, India stressed that live vaccines — which use live rather than killed bacteria — have an edge over existing vaccines that require two doses.

In addition, existing vaccines only give short-term protection against cholera, lasting only about six months.

"Since an oral live vaccine can give rapid immunity after a single dose, a vaccine like Peru-15 would be most useful in developing countries like Bangladesh and India as a public health tool during cholera epidemics," said Chatterjee.

However, live vaccines can be shed and infect non-vaccinated subjects, making them difficult to licence. "The vaccine here seems to have overcome this problem," says Bohumil Drasar, emeritus professor of bacteriology at the UK-based London School of Hygiene and Tropical Medicine.

Research is underway to make this vaccine easy to distribute, so that it can survive for a few days without cold storage. "This should make it convenient for use during emergencies," says Sack.

The research will be published online in the journal Vaccine on 11 December.

Reference: Vaccine doi: 10.1016/j.vaccine.2006.08.031 (2006)