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Cholera reproduction rates by Department, higher figures indicate faster spread of the disease.  Bringing these numbers to less than 1 would mean the epidemic is being suppressed. Cholera reproduction rates by Department, higher figures indicate faster spread of the disease. Bringing these numbers to less than 1 would mean the epidemic is being suppressed. Zindoga Mukandavire, David L. Smith & J. Glenn Morris Jr

 

Study suggests effectiveness of cholera vaccination in Haiti

The cholera epidemic in Haiti, which has caused over 7,700 deaths in the country since the disease first appeared in 2010, has been the focus of many initiatives by international NGOs, universities and governments, as well as the UN.  After more than two years these stakeholders are still struggling to find the appropriate balance between meeting immediate needs and building long-term solutions.

While eradication of the disease will depend on improved sanitation and water treatment infrastructure, the most effective short-term response has been a point of debate among many of the institutions involved these efforts.  A new study by the University of Florida suggests that a vaccination campaign could prove a valuable tool in quelling the spread of the disease.

A two-dose oral cholera vaccine has seen a couple of trial campaigns in Haiti, on top of small- and large-scale experiences in places such as Mozambique, Zimbabwe, India, Vietnam and Bangladesh.  The vaccine, however, is not perfect, with even the most advanced versions showing an efficacy rate from 65 and 78%.  Doubts surrounding the effectiveness of such campaigns, and the time-tested effectiveness of other short-term measures such as sanitation facilities, handwashing stations, soap distribution and point-of-use water treatment like chlorination and boiling, have sidelined vaccination as a primary response in Haiti.

This latest study finds, however, that even with a limited coverage of 46% of the population, vaccination may be able to put cholera in check in Haiti.  The University of Florida researchers, which have a permanent public health lab in Haiti, used a mathematical model to estimate the effectiveness of vaccination by Department and on a nation-wide level.

Based on case data, the rate at which cholera is spread varies significantly from Department to Department, with Artibonite (a largely rural Department north of Port-au-Prince) having the highest rate.  But the way in which the disease spreads is also dramatically different, while human-to-human transmission accounting for about 68% of cases country-wide, environmentally-borne transmissions dominated in Artibonite, at 97%.  These data support previous studies concluding that the focal point of the epidemic was contaminated water in the Artibonite River.

Such wide-spread environmental contamination underscores the need for long-term water treatment and sanitation solutions.  Indeed, without such measures, gains from any vaccination campaign would be diminished as outbreaks are more likely to recur.

Although vaccination alone will not be enough to defeat cholera in Haiti, as evidenced by models as well as long-standing experience, this study indicates that it may be a viable option to sending the epidemic into regression.  That could offer much needed relief in the short-term, even considering the limited effectiveness of the vaccine and the likelihood of only moderate coverage.

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