Ever since cholera began sweeping through Haiti in October, health officials have been drilling home the importance of sanitation practices and clean drinking water for slowing spread of the deadly disease.
But there has been little talk of immunizing Haiti's population against cholera, even though there are two vaccines for the disease. The reason, according to health experts, is a global shortage of vaccine supply.
"We don’t even really have it as an option to consider," said Peter Hotez, president of the Sabin Vaccine Institute and the American Society of Tropical Medicine & Hygiene. "The supply is just so inadequate in terms of what's available now."
The Pan American Health Organization says 100,000 doses of the Swedish-made Dukoral cholera vaccine are currently available for shipment, which would cover 50,000 people (two doses are needed to provide protection). Another 1 million doses of Shanchol, a new, cheaper cholera vaccine produced in India, are stockpiled and could be shipped over the course of 2011, but the vaccine manufacturer would need to obtain an expedited approval from the WHO in order for international organizations to purchase it.
With more than 9 million people living in Haiti, and 10 million more in bordering Dominican Republic, the best-case scenario still falls woefully short of covering the population.
"Under no circumstances could there be enough vaccine-over 40 million doses-to vaccinate all the inhabitants of the island of Hispaniola over the next year," said Jon Andrus, PAHO's deputy director, at the conclusion of a high-level meeting on the issue in December.
He points to the fact that cholera usually affects very poor parts of the world, including Eastern and Sub-Saharan Africa and parts of Asia, creating little incentive for drug companies.
"Flu vaccine is a global strategy and there is a market for it, where with many diseases of poverty there is not that same market force driving the supply," Andrus said.
PAHO is now calling for the creation of an international stockpile of cholera vaccine, as well as a small pilot cholera vaccine project in Haiti to begin in spring of 2011 and expand as more vaccine is available.
Such a pilot project could provide valuable in-the-field expertise on how to deploy a cholera vaccine on a large scale, said Stephen Calderwood, chief of infectious disease at Massachusetts General Hospital, and a cholera expert who is collaborating on a field trial of Shanchol in Bangladesh.
"Haiti does represent an opportunity, if vaccine is available, to answer some of the public health questions about how to use the vaccine in the best way," he said.
Some of the concerns over the existing vaccines are that they provide only 60 to 80 percent protection, and last only two to three years, creating cost and logistical concerns over having to repeatedly immunize a population, said Calderwood. Dukol costs $40 per dose, while Shanchol, developed with a grant from the Bill and Melinda Gates Foundation*, is $6 a dose.
Full protection of the vaccine is also not conveyed until about three weeks after the first dose, and the need for a second dose creates complications in low-resource settings.
"We are still at the early stages of understanding how to use a vaccine like this in a reactive situation, after an epidemic has already broken out," said Hotez, of Sabin Vaccine Institute, which has no ties to the cholera vaccine manufacturers.
The need for this type of field expertise has been emphasized by recent cholera outbreaks in Angola, Ethiopia, Somalia, Sudan and Zimbabwe, which Hotez describes as "prolonged and protracted," raising the stakes for finding effective ways to respond with vaccines.
"We normally think of [cholera] as a short term problem that will burn itself out in a couple weeks, so a vaccine wouldn’t be appropriate," he said. "The length and scope of these epidemics has increased, so now it’s different."
*For the record, the Bill & Melinda Gates Foundation underwrites the NewsHour's global health coverage.
May 17, 2013
