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Potential cholera vaccine for travelers passes safety test


Researchers have tested a potential vaccine against cholera and found it to be safe and effective in a study population. The potential vaccine, called Peru-15, is being developed for use by persons who live outside regions affected by cholera, including travelers and military personnel. The safety test was the first step in evaluating Peru-15 as a potential vaccine, which then could also be used in areas where cholera is endemic, according to the researchers.

Cholera bacterium, Vibrio cholerae.

The oral vaccine was created from a strain of the bacterium Vibrio cholerae isolated in Peru in 1991 (the O1 El Tor Inaba strain). The researchers deleted a core group of genes that encode virulence factors and cholera toxins. This made Peru-15 less virulent and safe for testing in people.

None of the subjects in the study had previously been exposed to cholera. One of the challenges in creating a cholera vaccine is that the disease does not produce a clear and observable immune response. That is why scientists have to expose people to the cholera bacterium during trials and then monitor each person’s physical response and symptoms of the disease.

In the Peru-15 study, 59 volunteers were randomly assigned to either a placebo group or the vaccine group. After exposure to cholera, 42 percent of the volunteers in the placebo group developed moderate or severe cholera. Volunteers in the vaccinated group, however, did not experience the adverse effects of cholera, which include moderate and severe diarrhea.

“It had terrific protective efficacy,” says Mitchell B. Cohen, who led the study at the Children’s Hospital Medical Center in Cincinnati, Ohio. He adds that further studies must be conducted to determine the vaccine’s preparedness the market.

The vaccine may also contribute to the prevention of cholera in developing countries where the disease is endemic. “Data from this study suggest to us that Peru-15 is a strong candidate for further evaluation as a tool to prevent cholera in an area where cholera is endemic,” the researchers write in the journal Infection and Immunity. A large-scale field study of the vaccine in Bangladesh is currently under discussion.

The cholera bacterium infects the human intestine, where it causes severe and sometimes fatal dehydration from diarrhea. The disease can be treated effectively by re-hydration, but treatment facilities are often inaccessible and overcrowded in endemic areas.

See related GNN articles
»Cholera genome sequenced
»Comparative study reveals genes related to cholera pandemic

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Cohen, M.B. et al. Randomized controlled human challenge study of the safety, immunogenicity, and protective efficacy of a single dose of Peru-15, a live attenuated oral cholera vaccine. Infect Immun 70, 1965-1970 (April 2002).

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