Cholera today is more resilient than previous types, but as the world marks 50 years since the most recent strain surfaced, two studies this week suggest that vaccines can help even after an outbreak starts.

One of the studies in this week's Public Library of Science (PLoS) Neglected Tropical Diseases journal analyzed data from Zimbabwe, India and Tanzania to see how many cases could have been preventable under differing response times, vaccine dosage and coverage area.

In Zimbabwe, where a cholera outbreak began in August 2008 and lasted through July 2009, quick intervention could have saved many of the 4,288 lives lost.

"If a rapid response had taken place and half of the population had been vaccinated once the first 400 cases had occurred, as many as 34,900 (40%) cholera cases and 1,695 deaths (40%) could have been prevented," it said.

However in places like Kolata in India and Zanzibar in Tanzania which suffer from endemic cholera "the impact would have been less dramatic," the study said.

A second study examined the use of oral vaccines in Vietnam, and found that it was 76 percent protective against a cholera outbreak in Hanoi "after adjusting for intake of dog meat or raw vegetables and not drinking boiled or bottled water most of the time."

The research is particularly important because of the way the current type of cholera has evolved to become more resilient and deadly than its predecessors, said Edward Ryan, an infectious disease expert at Harvard University.

"We have a wily and adaptive foe that has changed the rules of engagement repetitively, and it may be time for us to similarly adapt our strategies," Ryan wrote in PLoS.

"Response efforts to cholera over the last 30 years have largely focused on treating individuals who become afflicted in the short-term, and trying to provide safe water and improved hygiene in the long-term," Ryan said.

"However, as we mark a half century for this pandemic, we must stop and ask: is this still the best approach?"

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