Health officials in Bangladesh are due to launch the world's largest trial of an affordable cholera vaccine which could save tens of thousands of lives.
The study involves nearly 250,000 people near the capital, Dhaka.
If the results are positive, the programme can be replicated in other countries where cholera is a big problem, officials say.
Cholera outbreaks every year during the monsoon season kill hundreds in Bangladesh.
But many oral vaccinations are considered too expensive for millions of people in this impoverished country.
The latest initiative aims to test an affordable version of an oral vaccination, which is one-tenth of the cost of the current available vaccines.
Two-thirds of the 250,000 people involved in the trial will receive two doses of the Indian-made vaccine.
'At high risk'
The remainder will not receive the medicine and the two groups will be monitored over the next four years.
"It is a study that will demonstrate that we can deliver the vaccine to the population that needs it the most, the people at high risk of cholera," Firdousi Qadri, one of the scientists involved in the project said.
"At the same time it will be a test of the existing immunisation mechanism that we have in this country," she said.
One of the broader aims of the project is to get a better idea of how many people die each year from cholera.
If the programme proves successful, then the authorities will go for a mass immunisation of the entire country.
The results are likely to trigger interest from other developing countries, like Haiti, which have had outbreaks of cholera.
But critics say that modern-day drugs do not offer long-term protection against every cholera strain.
Some experts say that along with mass vaccination, investments in improved water and sanitation infrastructure can help reduce the impact of cholera.