The program was launched in the slum area of Cite de Dieu, in the Haitian capital, where health practitioners are going door-to-door to deliver doses to pre-registered recipients.

"I am very happy that I received the vaccine because now I will live my life with less anxiety," Mariane Joseph told Reuters, after drinking the dose. "I have been waiting for this vaccine for a long time because we are exposed here to catching cholera."

More than 7,000 Haitians have died of cholera since an epidemic broke out in 2010.

The Director-General of the Health department, Dr. Gabriel Thimote, said the 100,000 beneficiaries in two regions in the west and northern Artibonite region will receive two doses of the vaccine, called Shanchol, that will protect them for two to three years with an efficiency rate of about 65 percent, health officials say.

"It is a pilot program that we are launching in two areas in the country but it will be later extended to the rest of the population with a priority for areas at risk," Thimote told Reuters.

In the capital, the program is being implemented by the Gheskio Center, a Haitian health NGO that specializes in fighting the AIDS virus and other infectious diseases, while another international NGO, Partners In Health, led by the U.N. deputy special envoy for Haiti, Dr. Paul Farmer, has been designated to carry out the vaccination program in Bokozel, near the northern town of St-Marc.

The Haitian health minister, Florence Duperval Guillaume, rejected allegations that the vaccine is experimental and could have side effects. The vaccination program was delayed several weeks after some critics suggested the campaign was a research project to test new, unapproved drugs.

"This is vaccine that has already been certified by the World Health Organization, and our campaign has nothing to do with an experimentation that could have recipients running risks," Guillaume said. "People have nothing to fear," she added.

Cholera is an infection that causes severe diarrhea that can lead to dehydration and death. It occurs in places with poor sanitation and can be treated by drinking clean fluids.

The number of cases has increased slightly in Haiti over the past few weeks, with frequent torrential rains spreading the bacteria in several areas where health official had brought the disease under control.

The Western Hemisphere's only cholera epidemic has infected nearly 550,000 and killed 7,400 people in Haiti and the neighboring Dominican Republic since October 2010 - with nearly all of the deaths in Haiti, according to the Centers for Disease Control and Prevention (CDC) in Atlanta.

Cases of cholera first emerged in central Haiti's Artibonite River region, possibly as a result of poor sanitary conditions at a U.N. base of peacekeepers from Nepal, where cholera is endemic. Haiti previously had no cases of cholera in recorded history.

Health workers continue to see 100-200 new cases per day, but that is far lower than then the 1,000 new cases a day they were seeing this time a year ago, said Dr. John Vertefeuille, the CDC country director in Haiti.

Daily numbers can vary according to "seasonal patterns," he added, and could rise during the rainy season. "We are still in the relatively early stages of this epidemic," he said, noting that "the goal is to eliminate cholera (in Haiti) over a 10-year period."

(Additional reporting by David Adams; Editing by David Adams and Philip Barbara)

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