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An India-made cholera vaccine that meets World Health Organization standards has proven to be safe and effective in young children in a part of India where the disease is endemic, a new study says.

The researchers, who published their study results in The Lancet, hope the vaccine can soon be rolled out in developing countries where cholera remains endemic.

The trial involved 107,774 participants in Kolkata in eastern India, half of whom were given the vaccine and the other half a placebo -- a lookalike with no therapeutic value.

The vaccine was orally administered in two doses, at least 14 days apart, and the researchers tracked the participants for two years.

On average, there were 20 episodes of cholera in the vaccine group and 68 episodes in the placebo group, which meant the vaccine had a protective efficacy rate of 67 percent, the researchers said. There were no adverse events linked to the vaccine.

This ... trial shows that the modified killed-whole-cell oral vaccine is safe and efficacious, providing nearly 70 percent protection against clinically significant cholera for at least 2 years after vaccination, wrote the researchers, led by John Clemens at the International Vaccine Research Institute (IVI) in Seoul, South Korea.

Protection was seen in children vaccinated at ages under 5 years, as well as in older individuals.

An earlier version of this vaccine has been used in Vietnam. Though it is effective, it has never been approved for use elsewhere because the manufacturing process in Vietnam did not reliably remove cholera toxin from the vaccine, the researchers said.

Furthermore, Vietnam's national regulatory authority is not WHO-approved.

IVI worked with Vietnamese manufacturer VaBiotech to improve the vaccine and production has since been transferred to vaccine maker Shantha Biotechnics in Hyderabad in India, where the national regulatory authority is WHO-approved.

Cholera causes 120,000 deaths every year worldwide, according to the WHO.