World's cholera vaccine stash is empty-but relief is on its way

A dramatic shortage of the oral vaccine may ease in the years ahead as more companies enter the market.

Global oral cholera vaccine use, 2013-2018

Vaccination is a key intervention to prevent and control cholera in conjunction with water, sanitation and hygiene activities. An oral cholera vaccine (OCV) stockpile was established by the World Health Organization (WHO) in 2013. We reviewed its use from July 2013 to all of 2018 in order to assess its role in cholera control. We computed information related to OCV deployments and campaigns conducted including setting, target population, timelines, delivery strategy, reported adverse events, coverage achieved, and costs. In 2013-2018, a total of 83,509,941 OCV doses have been requested by 24 countries, of which 55,409,160 were approved and 36,066,010 eventually shipped in 83 deployments, resulting in 104 vaccination campaigns in 22 countries. OCVs had in general high uptake (mean administrative coverage 1st dose campaign at 90.3%; 2nd dose campaign at 88.2%; mean survey-estimated two-dose coverage at 69.9%, at least one dose at 84.6%) No serious adverse events were reported. Campaigns were organized quickly (five days median duration). In emergency settings, the longest delay was from the occurrence of the emergency to requesting OCV (median: 26 days). The mean cost of administering one dose of vaccine was 2.98 USD. The OCV stockpile is an important public health resource. OCVs were generally well accepted by the population and their use demonstrated to be safe and feasible in all settings. OCV was an inexpensive intervention, although timing was a limiting factor for emergency use. The dynamic created by the establishment of the OCV stockpile has played a role in the increased use of the vaccine by setting in motion a virtuous cycle by which better monitoring and evaluation leads to better campaign organization, better cholera control, and more requests being generated. Further work is needed to improve timeliness of response and contextualize strategies for OCV delivery in the various settings.

High cholera vaccination coverage following emergency campaign in Haiti: Results from a cluster survey in three rural Communes in the South Department, 2017

Oral cholera vaccine (OCV) has increasingly been used as an outbreak control measure, but vaccine shortages limit its application. A two-dose OCV campaign targeting residents aged over 1 year was launched in three rural Communes of Southern Haiti during an outbreak following Hurricane Matthew in October 2016. Door-to-door and fixed-site strategies were employed and mobile teams delivered vaccines to hard-to-reach communities. This was the first campaign to use the recently pre-qualified OCV, Euvichol. The study objective was to estimate post-campaign vaccination coverage in order to evaluate the campaign and guide future outbreak control strategies.

We conducted a cluster survey with sampling based on random GPS points. We identified clusters of five households and included all members eligible for vaccination. Local residents collected data through face-to-face interviews. Coverage was estimated, accounting for the clustered sampling, and 95% confidence intervals calculated.

435 clusters, 2,100 households and 9,086 people were included (99% response rate). Across the three communes respectively, coverage by recall was: 80.7% (95% CI:76.8–84.1), 82.6% (78.1–86.4), and 82.3% (79.0–85.2) for two doses and 94.2% (90.8–96.4), 91.8% (87–94.9), and 93.8% (90.8–95.9) for at least one dose. Coverage varied by less than 9% across age groups and was similar among males and females. Participants obtained vaccines from door-to-door vaccinators (53%) and fixed sites (47%). Most participants heard about the campaign through community ‘criers’ (58%).

Despite hard-to-reach communities, high coverage was achieved in all areas through combining different vaccine delivery strategies and extensive community mobilisation. Emergency OCV campaigns are a viable option for outbreak control and where possible multiple strategies should be used in combination. Euvichol will help alleviate the OCV shortage but effectiveness studies in outbreaks should be done.

After Hurricane Matthew hit Southern Haiti on October 4, 2016, there was an outbreak of Cholera. The Government launched a campaign to vaccinate residents using an oral vaccine, which has been proven to protect people against the disease. MSF supported the campaign in three rural areas, offering the vaccine in local clinics and going from door to door. We didn’t know how many people were living there at the time so we couldn’t say for sure if we had vaccinated enough people. To find out how many people were vaccinated we did a survey, choosing households at random and asking them if and where they received the vaccine. This showed that on average around 90% of people were vaccinated, which is a very high proportion. We can take encouragement from this that mass vaccination campaigns like this can work well, even in rural settings. Our survey showed that about half of people got their vaccine from a clinic and the other half from door-to-door vaccinators, so it’s probably important to use both approaches. Most people heard about the campaign through members of the local community called ‘criers’. This shows how important it is to engage with the local community during a vaccination campaign.

Prolonging herd immunity to cholera via vaccination: Accounting for human mobility and waning vaccine effects

BACKGROUND

Oral cholera vaccination is an approach to preventing outbreaks in at-risk settings and controlling cholera in endemic settings. However, vaccine-derived herd immunity may be short-lived due to interactions between human mobility and imperfect or waning vaccine efficacy. As the supply and utilization of oral cholera vaccines grows, critical questions related to herd immunity are emerging, including: who should be targeted; when should revaccination be performed; and why have cholera outbreaks occurred in recently vaccinated populations?

METHODS AND FINDINGS

We use mathematical models to simulate routine and mass oral cholera vaccination in populations with varying degrees of migration, transmission intensity, and vaccine coverage. We show that migration and waning vaccine efficacy strongly influence the duration of herd immunity while birth and death rates have relatively minimal impacts. As compared to either periodic mass vaccination or routine vaccination alone, a community could be protected longer by a blended "Mass and Maintain" strategy. We show that vaccination may be best targeted at populations with intermediate degrees of mobility as compared to communities with very high or very low population turnover. Using a case study of an internally displaced person camp in South Sudan which underwent high-coverage mass vaccination in 2014 and 2015, we show that waning vaccine direct effects and high population turnover rendered the camp over 80% susceptible at the time of the cholera outbreak beginning in October 2016.

CONCLUSIONS

Oral cholera vaccines can be powerful tools for quickly protecting a population for a period of time that depends critically on vaccine coverage, vaccine efficacy over time, and the rate of population turnover through human mobility. Due to waning herd immunity, epidemics in vaccinated communities are possible but become less likely through complementary interventions or data-driven revaccination strategies.

Framework for Optimal Global Vaccine Stockpile Design for Vaccine-Preventable Diseases: Application to Measles and Cholera Vaccines as Contrasting Examples

Managing the dynamics of vaccine supply and demand represents a significant challenge with very high stakes. Insufficient vaccine supplies can necessitate rationing, lead to preventable adverse health outcomes, delay the achievements of elimination or eradication goals, and/or pose reputation risks for public health authorities and/or manufacturers. This article explores the dynamics of global vaccine supply and demand to consider the opportunities to develop and maintain optimal global vaccine stockpiles for universal vaccines, characterized by large global demand (for which we use measles vaccines as an example), and nonuniversal (including new and niche) vaccines (for which we use oral cholera vaccine as an example). We contrast our approach with other vaccine stockpile optimization frameworks previously developed for the United States pediatric vaccine stockpile to address disruptions in supply and global emergency response vaccine stockpiles to provide on-demand vaccines for use in outbreaks. For measles vaccine, we explore the complexity that arises due to different formulations and presentations of vaccines, consideration of rubella, and the context of regional elimination goals. We conclude that global health policy leaders and stakeholders should procure and maintain appropriate global vaccine rotating stocks for measles and rubella vaccine now to support current regional elimination goals, and should probably also do so for other vaccines to help prevent and control endemic or epidemic diseases. This work suggests the need to better model global vaccine supplies to improve efficiency in the vaccine supply chain, ensure adequate supplies to support elimination and eradication initiatives, and support progress toward the goals of the Global Vaccine Action Plan.

Efficacy and safety of a modified killed-whole-cell oral cholera vaccine in India: an interim analysis of a cluster-randomised, double-blind, placebo-controlled trial

BACKGROUND

Oral cholera vaccines consisting of killed whole cells have been available for many years, but they have not been used extensively in populations with endemic disease. An inexpensive, locally produced oral killed-whole-cell vaccine has been used in high-risk areas in Vietnam. To expand the use of this vaccine, it was modified to comply with WHO standards. We assessed the efficacy and safety of this modified vaccine in a population with endemic cholera.

METHODS

In this double-blind trial, 107 774 non-pregnant residents of Kolkata, India, aged 1 year or older, were cluster-randomised by dwelling to receive two doses of either modified killed-whole-cell cholera vaccine (n=52 212; 1966 clusters) or heat-killed Escherichia coli K12 placebo (n=55 562; 1967 clusters), both delivered orally. Randomisation was done by computer-generated sequence in blocks of four. The primary endpoint was prevention of episodes of culture-confirmed Vibrio cholerae O1 diarrhoea severe enough for the patient to seek treatment in a health-care facility. We undertook an interim, per-protocol analysis at 2 years of follow-up that included individuals who received two completely ingested doses of vaccine or placebo. We assessed first episodes of cholera that occurred between 14 days and 730 days after receipt of the second dose. This study is registered with ClinicalTrials.gov, number NCT00289224.

FINDINGS

31 932 participants assigned to vaccine (1721 clusters) and 34 968 assigned to placebo (1757 clusters) received two doses of study treatment. There were 20 episodes of cholera in the vaccine group and 68 episodes in the placebo group (protective efficacy 67%; one-tailed 99% CI, lower bound 35%, p<0.0001). The vaccine protected individuals in age-groups 1.0-4.9 years, 5.0-14.9 years, and 15 years and older, and protective efficacy did not differ significantly between age-groups (p=0.28). We recorded no vaccine-related serious adverse events.

INTERPRETATION

This modified killed-whole-cell oral vaccine, compliant with WHO standards, is safe, provides protection against clinically significant cholera in an endemic setting, and can be used in children aged 1.0-4.9 years, who are at highest risk of developing cholera in endemic settings.

FUNDING

Bill & Melinda Gates Foundation, Swedish International Development Cooperation Agency, Governments of South Korea, Sweden, and Kuwait.

Private demand for cholera vaccines in Hue, Vietnam

OBJECTIVES

This study aims to measure the private demand for oral cholera vaccines in Hue, Vietnam, an area of relatively low endemicity of cholera, using the contingent valuation method.

METHODS

Interviews were conducted with either the head of household or spouse in 800 randomly selected households with children less than 18 years old. Respondents were asked whether they would purchase an oral cholera vaccine with different levels of effectiveness and durations of effectiveness (both for themselves and for other household members) at a specified price.

RESULTS

The median respondent willingness to pay for 50% effective/3-year vaccine was estimated to be approximately $5, although 17% of the study sample would not pay for a cholera vaccine. The median economic benefit to a household of vaccinating all household members against cholera, as measured by its stated willingness to pay, was estimated to be $40 for a vaccine with these attributes.

CONCLUSIONS

The perceived private economic benefits of a cholera vaccine were high, but not evenly distributed across the population. A minority of the people in Hue place no value on receiving a cholera vaccine.

Private demand for cholera vaccines in rural Matlab, Bangladesh

OBJECTIVES

To estimate household willingness to pay (WTP) for cholera vaccines in a rural area of Bangladesh, which had participated in a 1985 oral cholera vaccine trial.

METHODS

A contingent valuation study was undertaken in Matlab, Bangladesh in summer 2005. All respondents (N=591) received a description of a cholera vaccine that was 50% effective for 3 years and had negligible side effects. Respondents were asked how many vaccines they would purchase for their household at randomly pre-assigned prices. Negative binomial regression models were used to estimate the number of vaccines demanded and to calculate average WTP.

RESULTS

On average, respondents were willing to pay about US$ 9.50 to purchase vaccines for all members of their household (i.e. US$ 1.70 per vaccine). Average WTP per person is US$ 2.40 for young children (1-4 years), US$ 1.20 for school-age children, and US$ 1.05 for adults. Median WTP estimates are significantly smaller: US$ 1.00 for young children, US$ 0.05 for schoolchildren, and US$ 0 for adults.

CONCLUSIONS

There is significant demand for cholera vaccines in Matlab at low prices. Recent herd protection research suggests that unvaccinated persons would also experience reduced incidence via indirect effects at low coverage rates associated with moderate vaccine prices.

The value of cholera vaccination in promoting travel health

Cholera is a diarrhoeal disease caused by intestinal infection with Vibrio cholerae bacterium (Health Protection Agency, 2004). Travellers are now able to obtain a cholera vaccine in the UK. Although cholera is rare in travellers from the UK, its potential severity is a cause for concern. Nurses will need to consider the availability of this new vaccine when providing health promotion to travellers.

[Anticholera vaccines and vaccination]

Cholera is still an important diarrhoeal disease in developing countries. The impact of cholera out-break is tremendous for a country at human and economic level. WHO estimates that diarrhoeal diseases cause about 2.8 million deaths per year in developing countries. Officially, cholera is causing around 120,000 deaths per year. The poorest population (from slums and refugee camps) are the most vulnerable target for cholera infection. Development of simple cheap and effective vaccine is highly recommended. This article aims at giving an update on the currently available and future vaccines for the prevention of diarrhoea due to Vibrio cholerae O1 and O139.