October 19, 2011

The consensus is that cholera has taken up a long-term, if not permanent, environmental presence in the country, and as such, the reinforcement and expansion of preventive measures has become vital.

Haiti was hit with a massive epidemic of cholera, a disease not seen in the country for perhaps a century, in October 2010. The causative pathogen, Vibrio cholerae—variant O1 Ogawa—has been imported and introduced by human activity.

The numbers of infected people across Haiti reached their peak by the last week of 2010, when over 4,000 cases of cholera were reported daily, according to the Haitian Ministry of Health. Subsequently, the number of cases declined slowly until the end of April 2011, with 500 cases reported daily. A second rise was reported and reached a peak in mid-June of 2,000 cases per day.  As of October 2011, more than 464,000 cases and 6,500 deaths have been recorded.

Cholera transmission in Haiti is now in its twelfth month and some communities are being affected for a second time. The consensus is that cholera has taken up a long-term, if not permanent, environmental presence in the country, and as such, the reinforcement and expansion of preventive measures has become vital.

Dr. David Olson, MSF medical advisor for diarrheal diseases, has been involved in MSF’s response to the epidemic from the beginning. Here he answers questions about the possibility of using cholera vaccines to address these needs.

What are the vaccination options available today against cholera?

Vaccines against cholera have existed for decades, first in injectable form used by travelers and the military. However, its side effects and limited effectiveness have made it inappropriate for mass vaccinations, and they are almost never used. 

More recently, oral vaccines (OCVs) have been developed and trialed in cholera-endemic settings. They have proven to be effective and virtually free of serious side effects. Though protective immunity seems to wane after two to three years, the World Health Organization (WHO) has recommended OCVs as one prevention tool, in addition to water and sanitation measures, for over 10 years.

Currently, there are two OCVs available: Dukoral, which is manufactured by biopharmaceutical company Crucell, has been on the market for over 20 years; and Shanchol, made by Shantha Biotech, was recently pre-qualified by the WHO. Both medicines require two doses, given two weeks apart, conferring immunity seven days after the second dose. Clinically speaking, one is not better than the other in terms of protective efficacy, which is about 70 percent over two years, as seen in clinical trials. However, Dukoral has to be mixed with a buffer before being swallowed, while Shanchol is just a couple of milliliters of solution that can be dropped into the mouth like a polio vaccine. Logistically, the latter would be easier, and it would be affordable at around $2 per dose.

Could a mass vaccination campaign stop the ongoing epidemics in Haiti?

Without improving access to clean water and proper sanitation, cholera will undoubtedly keep coming back. Today, nearly half of the population does not access potable water and more than 80 percent don’t have sanitation facilities. That basically means we have to consider nearly everybody at risk in Haiti for developing cholera. And vaccinating everybody, as the government initially requested, poses several problems.

One issue is the capacity of the manufacturers to make enough vaccines. We are talking about nearly 20 million doses, which are not currently available—even after combining the two manufacturers’ capacities.

Money is another big issue. The vaccines alone would cost up to $40 million if everyone were vaccinated, to which must be added logistics and human resources. Let’s not forget protective immunity appears to decline after only two or three years and be efficient for two-thirds of the people vaccinated. Money spent on vaccines should not come at the expense of money spent on permanent water and sanitation measures. 

How could cholera vaccination still be used in fighting the disease in Haiti?

A way to have a significant impact could be to look at who will not be able to benefit from access to medical services or prevention measures.

In the urban environment, it is probably easier to deliver treatment and provide water, soap, and information. It’s much harder in mountainous or rural areas when cholera gets there. It won’t be easy to vaccinate in rural areas with poor access, but it would be even harder to intervene should an outbreak occur.

But it’s not MSF’s responsibility to make that choice. There is always a lot of pressure around who gets to be vaccinated. It needs input from the government. Vaccination is often as much a political act as a medical act.

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