Bangladesh holds world's largest trial of an oral cholera vaccine. This vaccination program could save thousands of lives every year, health officials said.
The World Health Organization estimates that up to five million people worldwide contract cholera each year, with 120,000 of them dying as a result.
And while oral vaccines have long been available, they are considered too expensive to employ on a wide scale, according to health authorities.
The study involves 240,000 people from Mirpur, one of Dhaka's poorest suburbs, two thirds of whom will receive two doses of the cheap Indian-made vaccine.
The remaining 80,000 people will not receive the vaccine. Both the control group and those who are given the liquid vaccine will be monitored over the next four years.
The study will determine whether the drug is rolled out in a state-backed mass vaccination, with the results likely to spark interest from other poor countries such as Haiti, where a recent cholera epidemic has killed over 4,000.
"It's the biggest cholera vaccination study in the world," said Nasmeen Ahmed of the International Center for Diarrhoeal Diseases Research, Bangladesh (ICDDR'B), which is running the scheme with the government.
"A successful outcome could prompt governments in countries where cholera has been a big health problem to go for a mass vaccination drive," she said.
"It is a critical study to know how a government can vaccinate millions of people against cholera."
The ICDDR'B was set up in the 1960, when cholera was still one of the leading causes of death in Bangladesh.
Nasmeen said the institute was carrying out the study in Mirpur because almost a quarter of cholera patients who come to the ICDDR'B clinic every year are from the impoverished area.
Poor sanitation, lack of clean water and vast slums in Mirpur make it vulnerable to cholera outbreaks.