Oral cholera vaccine effective for outbreak control

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1. The Shanchol oral cholera vaccine was effective at preventing cholera in the setting of an outbreak in Guinea. 

Evidence Rating Level: 3 (Average) 

Study Rundown: The Shanchol oral cholera vaccine has only been evaluated for long-term protection against cholera. It is not clear how protective the vaccine is within the first few months after administration.

This study evaluated the short-term efficacy of Shanchol in the setting of a cholera outbreak in Guinea between May and October 2012. The results of this case-control study showed that complete vaccination (two doses of vaccine) conferred 86.6% protection against cholera. This is similar to the protection conferred by Dukoral, the other oral cholera vaccine. Dukoral was shown to confer 84% protection in a similar case-control study of an outbreak in Mozambique.

These results may influence vaccine stockpiling decisions as Shanchol is cheaper and easier to store than Dukoral.

Click to read the study, published today in NEJM

Relevant Reading: Effectiveness of mass oral cholera vaccination in Beira, Mozambique

In-Depth [case-control]: This study took advantage of mass vaccination campaigns conducted in two prefectures in Guinea in response to a cholera outbreak beginning in February 2012. Forty cases of cholera were identified among the patients who presented to local health centers with acute watery diarrhea within a 3-4 month period after the mass vaccinations. One hundred and sixty age and gender-matched neighborhood controls (people without diarrheal illness) were also recruited. The odds of vaccination were compared between cases and controls to determine the effectiveness of vaccination.

The authors also included a bias-indicator subanalysis to determine whether differences in health-seeking behavior could account for their results. For this, they compared odds of vaccination among patients with non-cholera diarrheal disease and controls without diarrheal disease. There was no significant difference, suggesting it is not the case that individuals who get diarrheal illnesses are simply less likely to seek vaccination.

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