In the wake of one of the worst cholera outbreaks in more than a decade in Africa and the availability of effective vaccines, a group of international experts has called on the world health community to consider introducing oral cholera vaccines as a potential emergency measure to tackle the deadly diarrheal disease. 

In a policy paper published in the May 15 issue of the journal Science, the experts, including Dr. John Clemens, Director-General of the IVI, and Prof. Robert Black of  the Bloomberg School of Public Health at Johns Hopkins University in the United States, suggest that it may be time for the world to consider the use of oral cholera vaccines as another option for containing cholera outbreaks.

Cholera remains an important public health problem in the developing world, with as many as 120,000 deaths estimated to occur each year from the disease. A recent outbreak in Zimbabwe has killed at least 4,200 individuals since last August.

The cholera control strategy for outbreaks has changed little during the past decades. Oral rehydration therapy (ORT) and intravenous rehydration therapy has been the centerpiece for rehydrating people infected with cholera. Provision of safe water and adequate sanitation are widely employed as emergency measures for people at immediate risk of cholera infection, but are not guaranteed to remain once the outbreak ends.

An oral cholera vaccine called ‘rBS-WC,’ evaluated in Mozambique by the IVI in 2004, showed about 90 percent protection against cholera of life-threatening severity, even in a population with a high HIV prevalence. The vaccine is internationally licensed and available, and has also been shown to protect unvaccinated neighbors of vaccinees through “herd protection” against cholera.

Nevertheless, vaccination has not been recommended by the World Health Organization (WHO) as a strategy to contain cholera in Zimbabwe due to its two dose regimen, short shelf-life, high cost, and need for cold chain distribution. There are logistical complexities to administering a two-dose regimen in a setting as chaotic as Zimbabwe, as well as strategic choices to be made for how to target high risk groups for vaccination. But delivery of this vaccine has been shown to be feasible in three WHO-sponsored community demonstration projects in rural and urban sub-Saharan Africa.

Moreover, a potentially cheaper vaccine, which was developed by the IVI in collaboration with VaBiotech in Vietnam, was licensed in India last February (read a related story). The vaccine’s licensure in India, which has met WHO requirements, paves the way for worldwide use of the world’s first low-cost cholera vaccine that is suitable for use in developing countries, where most cholera cases occur.

Dr. Clemens said, “If current barriers to potential use of oral cholera vaccines could be overcome, public health workers, Ministries of Health, international organizations and donor groups could begin a constructive discussion about how, when, and where the vaccine could be deployed.”