Haiti is suffering the world's worst cholera epidemic, killing more than 7,000 people since the outbreak began in October 2010. One aid group is pushing for a vaccination campaign. But critics worry about its efficacy — and that it may distract from improving access to clean water and sanitation.

The cholera outbreak in Haiti is currently the worst ongoing episode in the world.

Over the last 15 months, it has sickened more than half a million people and killed roughly 7,000. The bacteria has now spread throughout the Caribbean island, and medical experts say it will be around for years to come.

Partners in Health, a Boston-based nonprofit, is planning to launch an unprecedented cholera vaccination campaign to try to curb the outbreak — but it faces many challenges, including a shortage of the vaccine.

For decades, Haiti had been considered a potential cholera flashpoint. Even before the 2010 earthquake, roughly 50 percent of Haitians lacked access to clean water and 80 percent didn't have adequate sewage systems, according to the World Health Organization.

Danger In The Slums

Antonina Tanis lives in the Port-au-Prince slum of Cite Soleil. The 56-year-old says there are no toilets in her neighborhood.

"We don't have no toilet at all. We do it in the sea," she says.

By "the sea," Tanis is referring to brackish tidal canals that flush in and out of the slum. Residents perch on a cement ledge over one of the canals when they have to relieve themselves. Cite Soleil is also known for "flying toilets," a practice of going to the bathroom in a plastic bag and then letting it "fly" out the window.

Ever since cholera appeared in Haiti in October 2010, it's been rampant in Cite Soleil. Tanis came down with it in November 2011. She says the vomiting hit her so hard by she couldn't even stand up.

"I was totally out of it," Tanis recalls. "I couldn't stand. I'd stand and I'd fall back down. I was dehydrated and about to die."

Her neighbors carried her to a nearby cholera treatment clinic, and within a week, she completely recovered.

Thousands of others in Haiti haven't been so fortunate. Several of Tanis' neighbors recount how their kids, wives or parents died from the disease.

Outbreak's Origins

Jon Lascher, Haiti program manager for Partners in Health, says the cholera outbreak began miles away, on Haiti's Central Plateau.

"This is where cholera started. The first cases tested positive for cholera in Mirebalais," Lascher says.

The group's cholera treatment center in Mirebalais is little more than a glorified tent filled with rows of tarp-covered beds.

"When there was a peak of cholera, we were seeing up to 100 patients a day at this facility," he says.

The number of patients has fallen dramatically recently but is expected to spike again when the rainy season returns.

The cholera outbreak began near a United Nations peacekeeping base housing Nepalese soldiers. The strain of cholera that raced across Haiti is nearly identical to the predominant strain in Southeast Asia.

It's widely believed in Haiti that overflowing outhouses at the U.N. compound were the source of the deadly outbreak. An independent study published by the Centers for Disease Control and Prevention drew a similar conclusion.

Questions Surround Vaccine Program

In the coming weeks, Partners in Health plans to launch an unprecedented — and somewhat controversial — vaccination campaign against the disease.

Lascher says ultimately the way to eliminate cholera from Haiti is through building water and sewage treatment systems, but he says that could take years.

"While we are waiting, we know that there's a safe and effective oral cholera vaccine that can help prevent people from getting cholera again. Why wouldn't we do that? I think it would be certainly expected anywhere else in the world," he says.

But the vaccination proposal has been criticized by some Haitians and questioned by other aid agencies.

Partners in Health is planning to use a relatively new vaccine, Shanchol. And because of limited global supply of the drug, as well as logistical concerns, Partners in Health is only planning to offer it to 100,000 people — or just 1 percent of the Haitian population.

The Platform of Haitian Human Rights Organizations issued a statement in December saying the money for a vaccine campaign should be invested instead in upgrading water and sewage systems.

Wendy Lei, the medical director in Haiti for the Swiss arm of Doctors Without Borders, says her group has decided not to participate in the vaccine campaign.

"My concern is that when people talk about vaccines, they think it's going to be a magic bullet. Wipe out cholera forever," Lei says. "Some vaccines are like that — smallpox, for instance. But the cholera vaccine is not like that."

According to the World Health Organization, Shanchol's efficacy rate ranges from 45 percent to 86 percent. And people immunized with Shanchol would need to be revaccinated every two or three years.

Lei questions how effective this limited campaign will be and says she is concerned it could be a distraction.

"You know, the best vaccine for cholera is water and sanitation system," she says.

Another issue is that Haiti has a very poor record when it comes to immunization campaigns.

Coverage rates in Haiti for established, routine vaccines such as measles, rubella and polio are extremely low.

Clean Water, Sanitation Still Top Priorities

The country director for the CDC, John Vertefeuille, says public health experts are very interested in seeing how this vaccine campaign goes.

"Cholera vaccine has never been used in an acute, ongoing epidemic of cholera, so there are some ongoing questions about how effective the vaccine will be in this population," he says.

He says the CDC supports the vaccination drive, but he adds that improving Haitians' access to treated water and sanitation remain the top priorities in the current outbreak.

Partners in Health officials say the bottom line for them is that the cholera vaccine is one more tool that could save lives. And they plan to start the first round of vaccinations in March. [Copyright 2012 National Public Radio]