Endemic cholera, a potentially fatal diarrheal disease found in the world's poorest countries, could be effectively controlled by orally vaccinating half of the affected populations once every two years for only pennies per dose, according to new findings by an international team of researchers.  The conclusion is based on a computer model of the vaccine's effectiveness.  VOA's Jessica Berman reports.

Cholera causes massive fluid loss that can kill.  While oral rehydration therapy has made the disease treatable, each year an estimated 100,000 to 500,000 people die from it.

Cholera is caused by ingesting contaminated food or water. 
For years, Western travelers to cholera-endemic countries have been offered an oral vaccine to protect them, but the drugs have never been used in epidemics, partly because of questions about their effectiveness.  But a new study suggests the oral cholera vaccine is highly effective in controlling outbreaks. 

Ira Longini is a statistician with the Fred Hutchinson Cancer Research Center in Seattle, Washington, and the study's lead author. 

"We really believe that cholera, which is on the move throughout the planet, is very controllable with very cheap and effective vaccines [that] are there," Longini said.

Using the results from a large-scale trial involving 200,000 women and children in a rural area of Bangladesh between 1984 and 1989, researchers from the United States,  South Korea, and India created a computer model to predict the effectiveness of the cholera vaccine.

According to the model, if 50 percent of the people who live in a high-risk community receive the cholera vaccine once every two years, Longini says the number of new cholera cases would be reduced by 90 percent, to less than one case in a thousand unvaccinated people.

That is because the vaccine against cholera confers what one researcher described as "herd immunity" - protection of non-vaccinated neighbors of vaccinated persons.

The study is published in the on-line journal Public Library of Science.

Longini says immunizing people with a cheap oral cholera vaccine would be easy.

"We have very good prediction[s] about where cholera transmission is likely to occur, so, you could really have it focused where cholera is and just concentrate on those populations," Longini said.

The study was supported by the South Korean International Vaccine Institute, with ties to the World Health Organization, and the Bill and Melinda Gates Foundation, which supports global health programs.