Evaluating the costs of cholera illness and cost-effectiveness of a single dose oral vaccination campaign in Lusaka, Zambia

Coverage survey and lessons learned from a pre-emptive cholera vaccination campaign in urban and rural communities affected by landslides and floods in Freetown Sierra Leone

BACKGROUND

On 14 August 2017, massive landslides and floods hit Freetown (Sierra Leone). More than 1,000 people lost their lives while approximately 6,000 people were displaced. The areas most affected included parts of the town with challenged access to basic water and sanitation facilities, with communal water sources likely contaminated by the disaster. To avert a possible cholera outbreak following this emergency, the Ministry of Health and Sanitation (MoHS), supported by the World Health Organization (WHO) and international partners, including Médecins Sans Frontières (MSF) and UNICEF, launched a two-dose pre-emptive vaccination campaign using Euvichol™, an oral cholera vaccine (OCV).

METHODS

We conducted a stratified cluster survey to estimate vaccination coverage during the OCV campaign and also monitor adverse events. The study population - subsequently stratified by age group and residence area type (urban/rural) - included all individuals aged 1 year or older, living in one of the 25 communities targeted for vaccination.

RESULTS

In total 3,115 households were visited, 7,189 individuals interviewed; 2,822 (39%) people in rural and 4,367 (61%) in urban areas. The two-dose vaccination coverage was 56% (95% confidence interval (CI): 51.0-61.5), 44% (95%CI: 35.2-53.0) in rural and 57% (95%CI: 51.6-62.8) in urban areas. Vaccination coverage with at least one dose was 82% (95%CI: 77.3-85.5), 61% (95%CI: 52.0-70.2) in rural and 83% (95%CI: 78.5-87.1) in urban areas.

CONCLUSIONS

The Freetown OCV campaign exemplified a timely public health intervention to prevent a cholera outbreak, even if coverage was lower than expected. We hypothesised that vaccination coverage in Freetown was sufficient in providing at least short-term immunity to the population. However, long-term interventions to ensure access to safe water and sanitation are needed.

Oral Cholera Vaccine Efficacy and Effectiveness

Although measuring vaccine efficacy through the conventional phase III study design, randomized, double-blinded controlled trial serves as the "gold standard", effectiveness studies, conducted in the context of a public health program, seek to broaden the understanding of the impact of a vaccine in a real world setting including both individual and population level impacts. Cholera is an acute diarrheal infection caused by the ingestion of food or water contaminated with the bacterium Vibrio cholerae. Since the 1980s, either killed or live oral cholera vaccines (OCVs) have been developed and efficacy and effectiveness studies have been conducted on OCV. Although the results of OCV effectiveness studies sometimes showed outliers, the tendency seen is for effectiveness of the vaccine used in public health settings to be somewhat higher than estimated in randomized controlled trials due to the influence of indirect herd protection. Efficacy and Effectiveness studies both generate important information about the vaccine performance characteristics and its impact when used in real world populations at risk for the disease.

Optimizing immunization schedules in endemic cholera regions: cost-effectiveness assessment of vaccination strategies for cholera control in Bangladesh

This study is to examine the cost-effectiveness of deployment strategies of oral cholera vaccines (OCVs) in controlling cholera in Bangladesh. We developed a dynamic compartment model to simulate costs and health outcomes for 12 years for four OCVs deployment scenarios: (1) vaccination of children aged one and above with two doses of OCVs, (2) vaccination of population aged 5 and above with a single dose of OCVs, (3) vaccination of children aged 1-4 with two doses of OCVs; and (4) combined strategy of (2) and (3). We obtained all parameters from the literature and performed a cost-effectiveness analysis from both health systems and societal perspectives, in comparison with the base scenario of no vaccination.The incremental cost-effectiveness ratios (ICERs) for the four strategies from the societal perspective were $2,236, $2,250, $1,109, and $2,112 per DALY averted, respectively, with herd immunity being considered. Without herd immunity, the ICERs increased substantially for all four scenarios except for the scenario that vaccinates children aged 1-4 only. The major determinants of ICERs were the case fatality rate and the incidence of cholera, as well as the efficacy of OCVs. The projection period and frequency of administering OCVs would also affect the cost-effectiveness of OCVs. With the cut-off of 1.5 times gross domestic product per capita, the four OCVs deployment strategies are cost-effective. The combined strategy is more efficient than the strategy of vaccinating the population aged one and above with two doses of OCVs and could be considered in the resource-limited settings.

Pharmacoeconomics in Africa: needs, prospect and challenges

Africa as a continent has experienced a continuous increase in the cost of healthcare as its demands increase. With many of these African countries living below the poverty threshold, Africans continue to die from preventable and curable diseases. Population increases have led to an increase in demands for healthcare, which unfortunately have been met with inequitable distribution of drugs. Hence, the outcomes from healthcare interventions are frequently not maximized. These problems notably call for some economic principles and policies to guide medication selection, procurement, or donation for population prioritization or health insurance. Pharmacoeconomics drives efficient use of scarce or limited resources to maximize healthcare benefits and reduce costs. It also brings to play tools that rate therapy choice based on the quality of life added to the patient after a choice of intervention was made over an alternative. In this paper, we commented on the needs, prospect, and challenges of pharmacoeconomics in Africa.

Model-based estimation of the economic burden of cholera in Africa

OBJECTIVES

To estimate the economic burden of cholera in Africa.

SETTINGS

Cholera affected 44 countries in Africa.

PARTICIPANTS

The analysis used data from public sources in Africa published until September 2019.

METHODS

Based on existing data from field-based cost-of-illness studies, estimated cholera incidence rates, and reported cholera cases to WHO, this research estimates the economic burden of cholera in Africa from a societal perspective with 2015 as the base year. The estimate included out-of-pocket costs, public health system costs, productivity loss related to illness and an optional productivity loss related to premature deaths valued by the human capital approach. As various input data such as cholera incidence, hospitalisation rates and the number of workdays lost were not well defined, a series of scenario analyses and uncertainty analyses, accounting for unknowns and data variability, was conducted. Similarly, the value of time lost due to illness and deaths using the human capital approach was explored through scenario analyses.

RESULTS

In 2015, an estimated 1 008 642 cases in 44 African countries resulted in an economic burden of US$130 million from cholera-related illness and its treatment. When the estimated 38 104 cholera deaths were included in the analysis, the economic burden increased to US$1 billion or international $2.4 billion for the same year. At the same time, when only the 71 126 cases and 937 deaths reported to the WHO are considered, the economic burden was only US$68 million for the year 2015. The estimates of economic burden are thus heavily dependent on the cholera incidence rate, how time lost due to illness and deaths are calculated, hospitalisation rates and hospitalisation costs.

CONCLUSION

The findings can be used as an economic justification for cholera control in Africa and for generating value-for-money evidence to underpin Ending Cholera-A Global Roadmap to 2030 with considerations to study limitations.

Cost-effectiveness of a reactive oral cholera immunization campaign using Shanchol™ in Malawi

Background

Oral cholera vaccines (OCV) have been recommended as additional measures for the prevention of cholera. However, little is known about the cost-effectiveness of OCV use in sub-Saharan Africa, particularly in reactive outbreak contexts. This study aimed to investigate the cost-effectiveness of the use of OCV Shanchol in response to a cholera outbreak in the Lake Chilwa area, Malawi.

Methods

The Excel-based Vaccine Introduction Cost-Effectiveness model was used to assess the cost-effectiveness ratios with and without indirect protection. Model input parameters were obtained from cost evaluations and epidemiological studies conducted in Malawi and published literature. One-way sensitivity and threshold analyses of cost-effectiveness ratios were performed.

Results

Compared with the reference scenario i.e. treatment of cholera cases, the immunization campaign would have prevented 636 and 1 020 cases of cholera without and with indirect protection, respectively. The cost-effectiveness ratios were US$19 212 per death, US$500 per case, and US$738 per DALY averted without indirect protection. They were US$10 165 per death, US$264 per case, and US$391 per DALY averted with indirect protection. The net cost per DALY averted was sensitive to four input parameters, including case fatality rate, duration of immunity (vaccine’s protective duration), discount rate and cholera incidence.

Conclusion

Relative to the Malawi gross domestic product per capita, the reactive OCV campaign represented a cost-effective intervention, particularly when considering indirect vaccine effects. Results will need to be assessed in other settings, e.g., during campaigns implemented directly by the Ministry of Health rather than by international partners.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12962-021-00270-y.