Abba, K., Graves, P.M., Sinclair, D., Zaman, K., Qadri, F.
Cholera is a cause of acute watery diarrhea, which can cause dehydration and death if not adequately treated. It usually occurs in epidemics, and is associated with poverty and poor sanitation. Effective, cheap, and easy to administer vaccines could help prevent epidemics. This complex review prepared by David Sinclair and co-authors examines data from 39 trials of currently available oral killed whole cell vaccines. Seven large trials evaluated cholera vaccines in endemic areas, four small studies evaluated the vaccines where participants are purposefully exposed to cholera infection, and a further 29 small trials examined data on safety. The review shows that the available vaccines can prevent 50% to 60% of cholera episodes for the first 2 years after vaccination. Protection is unlikely to last beyond 3 years and booster doses will be needed. The vaccines were shown to be quite safe and did not cause more side effects than placebo. Overall the methodological quality of the trials was good, meaning that there is a high degree of confidence in these results. The authors conclude that the impact and cost-effectiveness of including oral cholera vaccines into the routine vaccination schedule of endemic countries will depend on the prevalence of cholera, the frequency of epidemics, and access to basic health services that can provide rapid rehydration therapy. There isn't much data regarding the use of cholera vaccines in emergency and epidemic situations, but it is likely that they would have an important impact on reducing disease in epidemics, especially where access to clean water and sanitation is difficult to achieve.