Personal ViewThe scenario approach for countries considering the addition of oral cholera vaccination in cholera preparedness and control plans
Introduction
Responding to cholera outbreaks is challenging, since these life-threatening events can spread rapidly through populations and often occur in areas with the least health resources and poorest water and sanitation infrastructure. In parallel with timely treatment, access to potable water, food hygiene, adequate sanitation, and community engagement, WHO recommends that oral cholera vaccination be considered in areas where the disease is endemic (with seasonal peaks), as part of the response to outbreaks, or in a humanitarian crisis during which the risk of cholera is high,1 but the global supply of the vaccine is small compared with the population at risk for cholera.
Two internationally available and WHO-prequalified oral cholera vaccines are on the market.2 The first is an inactivated vaccine containing killed whole cells of Vibrio cholerae O1 with recombinant B subunit of cholera toxin marketed as Dukoral (Valneva, Sweden), which was prequalified in 2001. The second, prequalified in 2011, is a bivalent inactivated vaccine containing killed whole-cells of V cholerae O1 and V cholerae O139 and marketed as Shanchol (Shantha Biotechnics, Sanofi). Both Dukoral and Shanchol are given in two doses and confer direct and indirect (herd) immunity. Dukoral may be given to individuals aged 2 years and older and is taken with a bicarbonate buffer. Shanchol may be given to those aged 1 year and older, does not require a buffer, is less complicated to deliver, and is cheaper than Dukoral.2
Shanchol is available through a WHO oral cholera vaccine stockpile, which was created in 2012.3, 4 Currently, nearly all available Shanchol doses are in the stockpile and reserved for use in outbreaks or complex emergencies. There is increasing experience on oral cholera vaccine deployment,5 but no consensus exists on where and when to use the limited doses available in the best way. Cholera epidemiology varies greatly by region, affecting different age groups and different populations during varying time periods. Considering the oral cholera vaccine shortage, funding scarcity, and the presence of competing vaccination priorities, specific recommendations about when to consider oral cholera vaccines would be useful. A WHO decision-making tool is available that helps practitioners decide when oral cholera vaccines should be used in complex emergency situations, during cholera outbreaks, and in endemic settings,6, 7 but it does not provide specific recommendations.
The absence of detailed guidelines is understandable considering the difficulty of predicting cholera outbreaks and the challenges of implementing mass vaccinations in many areas where the disease occurs. We have developed a scenario approach that systematically classifies situations in which oral cholera vaccination might be useful. Our scenario approach distinguishes between five types of cholera epidemiology based on experiences from around the world. Each scenario, with examples, is described, followed by our recommendation for oral cholera vaccination. The scenarios and recommendations are summarised in the table. More than one scenario can describe a particular area and a scenario can evolve into another over time. This approach is by no means final, but we hope that it can start to build consensus on how and where oral cholera vaccination would be most useful.
Section snippets
Five cholera scenarios and recommendation for oral cholera vaccine use
When using the scenario approach, we need as much information as is available from the affected area about cholera cases, cholera deaths, diarrhoeal disease management, population displacement, access to treatment, water and sanitation problems, and the capacity to solve these problems. The minimum requirements for accessing vaccine from the stockpile include reporting of a culture-confirmed cholera outbreak, submission of a completed request form and accompanying annexes, submission of a
Discussion
The availability of an affordable cholera vaccine and the creation of a vaccine stockpile have generated an opportunity for wider use of oral cholera vaccination. We propose here an approach that decision makers can use in different cholera situations. With additional experience in using this method, the scenario approach can be further revised and fine-tuned. Revision will be particularly relevant for some of the terms used to describe the different scenarios, which might be thought of as
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Cited by (12)
Global oral cholera vaccine use, 2013–2018
2020, VaccineCitation Excerpt :In 2013, WHO, with funding (i.e. vaccine costs and since 2016 operational costs for campaign implementation) from GAVI, the Vaccine Alliance, created an OCV stockpile to respond to emergency situations [14], including outbreaks and humanitarian crises [15–17]. The OCV stockpile is also used in non-emergency settings as one of the key strategies to contribute controlling cholera in endemic areas (i.e. “cholera hotspots”), [18,19]. Ideally, OCV should be used in conjunction with other preventative measures such as WASH interventions and social mobilization.
Model distinguishability and inference robustness in mechanisms of cholera transmission and loss of immunity
2017, Journal of Theoretical BiologyCitation Excerpt :Estimates of the length of immunity in the literature range widely from several months to three to ten years (Levine et al., 1981; King et al., 2008; Koelle and Pascual, 2004). Immunity to cholera is of particular interest given the recent and ongoing oral cholera vaccine campaigns worldwide, including in Haiti, Bangladesh, and Thailand (Tohme et al., 2015; O'Leary and Mulholland, 2015; Deen et al., 2016; Phares et al., 2016), which raise additional questions of how vaccine-derived immunity compares to immunity derived from infection. As modeling gains prevalence among policy makers in public health (Abrams et al., 2012; Moyer, 2014; Auchincloss and Roux, 2008; Grad et al., 2012; Lofgren et al., 2014; Lipsitch et al., 2011), comparative or ensemble modeling approaches have been increasingly viewed as a way to ensure that the results of parameter estimation, forecasting efforts, and the evaluation of intervention strategies are conserved across the range of realistic model structures (Koopman, 2004; Meza et al., 2014).
The corn smut-made cholera oral vaccine is thermostable and induces long-lasting immunity in mouse
2016, Journal of BiotechnologyCitation Excerpt :The emergence of large and prolonged outbreaks, particularly in sub-Saharan Africa, make WHO to reconsider the recommendation of not oral cholera vaccination once an outbreak had started (Bhattacharya et al., 2009). Therefore, the limited economic resources in the affected countries limit the current supply of cholera vaccines to implement national vaccination campaigns and are not sufficient to meet endemic and epidemic worldwide needs (Deen et al., 2015). Thus, the development of the research and development of new affordable vaccines is crucial to prevent cholera outbreaks.
Successful comeback of the single-dose live oral cholera vaccine CVD 103-HgR
2016, Travel Medicine and Infectious DiseaseCitation Excerpt :Cholera is in many parts of the world still endemic, causing epidemics and constituting repeatedly serious public health problems [1,2], such as the recent large and long-lasting outbreaks in Zimbawe [3] and Haiti [4]. Effective and easy to administer cholera vaccines are today in need more than ever, for populations in endemic areas and for outbreak interventions [5–7], as well as for travellers and aid workers at risk [8,9]. The use of the reactogenic and relative ineffective injectable cholera vaccines was stopped in the early 1970s [10].
Vibrio cholerae and cholera: A recent African perspective
2020, Current Microbiological Research in Africa: Selected Applications for Sustainable Environmental Management