Primary prevention

Water and sanitation measures

High-quality water, sanitation and sewage systems are essential public health measures in the control of all diarrhoeal diseases, including cholera.[43]​​ Even when treated piped water is available, outbreaks may still occur if chlorination is not adequate.[6][27][44][45]​​

Boiling or filtration of water locally is therefore needed. Governments should also be encouraged to ensure safe water supplies. Better preparedness for refugee situations, with latrines and anticipation of the need for active case finding, is essential for reducing the risk of a cholera outbreak.

Vaccination

Oral vaccines for cholera include killed whole-cell vaccines (e.g., Dukoral®, Shanchol®, Euvichol®, and mORCVAX®), and one live attenuated vaccine (Vaxchora®).[6][46][47][48][49][50][51] [ Cochrane Clinical Answers logo ] ​​​​​​ Only three oral vaccines are pre-qualified by the World Health Organization (WHO) for the prevention of cholera: Dukoral®, Shanchol®, and Euvichol®.[6]

There are two types of killed whole-cell vaccines: monovalent and bivalent. Monovalent Dukoral® contains Vibrio cholerae O1 (El Tor and classical biotypes) and a recombinant cholera B-toxin subunit. The bivalent vaccines Shanchol® and Euvichol® share the same formulation and contain killed whole cells of both V cholerae O1 (El Tor and classical biotypes) and O139 serogroups.[52] mORCVAX® is another formulation similar to Shanchol®, but is only licensed in Vietnam.

Oral vaccines demonstrate good protective efficacy against V cholerae O1.[53][54][55][56][57][58] They are given as 2 doses (although Dukoral® is given as 3 doses in children from 2-5 years) and provide approximately 70% protection for between 2 and 3 years (1 year for small children). Meta-analyses confirm a medium to high level of protection for at least 3 years for standard 2-dose regimens of killed whole-cell oral cholera vaccines, but they also show a similar, short-term protection from a single dose (with potential implications for outbreak management).[53][59]​​

The WHO recommends the use of oral killed whole-cell vaccines in endemic areas for cholera and to consider their use in high-risk areas.[60][61]​ In one large, cluster-randomised trial in an endemic setting in urban Bangladesh, Shanchol® was reported to provide a cumulative 2-year overall protection of 37% in the vaccination-only group, and 45% in the vaccination and behavioural change group.[50]

An oral cholera vaccine conferred herd (indirect) protection by interrupting transmission in an urban slum setting in India, indicating that high levels of vaccine coverage could provide even greater levels of total (direct plus indirect) protection in populations at risk.[62] In a review of 16 campaigns conducted in refugee camps or following natural disasters, during which more than 3 million doses of the two WHO pre-qualified oral cholera vaccines were administered, 2-dose coverage was estimated to be between 46% and 88% of the target population.[61]

The oral cholera vaccine should not be given at the same time or within 2 weeks of the oral polio vaccine.[63] Guidance and lessons around cholera vaccination in the field are available, including on the pre-emptive (following events increasing the risk of cholera outbreaks, such as natural disasters), reactive (to stop an outbreak), and preventive (in endemic areas) use.[63]

For travellers visiting endemic countries, oral vaccination is not routinely recommended to prevent cholera. However, it may be considered for individuals with an increased risk of cholera exposure (e.g., health and humanitarian work; prolonged stay; high transmission risk at destination), health complications (e.g., reduced immunity and chronic disease worsened by dehydration; remote areas with limited access to medical care), or other specific circumstances.[63][64][65]​ The US Centers for Disease Control and Prevention recommends cholera vaccination for people travelling to or living in areas of active cholera transmission.[66]

Dukoral® is available in a range of non-endemic countries, including Canada and the UK. The live attenuated oral vaccine, Vaxchora®, is approved for individuals aged 2 to 64 years in the US who are travelling to, or living in, an area of active cholera transmission (defined as a province, state, or other administrative subdivision within a country with endemic or epidemic cholera caused by toxigenic V cholerae O1, including areas with cholera activity within the last year that are prone to recurrence of cholera epidemics).[67]​ In Europe, Vaxchora® is approved for active immunisation against disease caused by V cholerae O1 in adults and children aged 2 years and older. The efficacy of this single-dose vaccine is estimated to be between 80% and 90% when tested with healthy volunteers who underwent oral challenge with V cholerae 01 strain 10 days, 3 months, and 6 months post-vaccine.[68][69]

Injected vaccines, although safe and fairly efficacious, are no longer the standard of care and are, therefore, no longer being developed.[70]

Secondary prevention

The World Health Organization (WHO) cholera outbreak control measures suggest active case finding, observation of family members for secondary cases, attention to careful handwashing with soap and water, and disinfection of the dead and their belongings with simple burial procedures.[44]​

WHO: Cholera outbreak toolbox Opens in new window

Chemoprophylaxis of unaffected contacts is probably not cost effective or efficacious because many cases are asymptomatic.[110] In addition, mass prophylaxis may lead to rising resistance rates in isolates, causing subsequent cases. However, one systematic review found a protective effect associated with chemoprophylaxis of household contacts of people with cholera, although the evidence came from trials that had a high level of bias.[111]

Reactive vaccination might target high-risk areas where few cases have occurred, as part of a wider outbreak response. However, it is likely to be less effective in locations where an outbreak has already occurred, since a large number of individuals might already be infected and might often be asymptomatic.[63]

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