Abstract
BackgroundSchistosomiasis is a neglected tropical disease, targeted by the World Health Organization for reduction in morbidity by 2020. It is caused by parasitic flukes that spread through contamination of local water sources. Traditional control focuses on mass drug administration, which kills the majority of adult worms, targeted at school-aged children. However, these drugs do not confer long-term protection and there are concerns over the emergence of drug resistance. The development of a vaccine against schistosomiasis opens the potential for control methods that could generate long-lasting population-level immunity if they are cost-effective.MethodsUsing an individual-based transmission model, matched to epidemiological data, we compared the cost-effectiveness of a range of vaccination programmes against mass drug administration, across three transmission settings. Health benefit was measured by calculating the heavy-intensity infection years averted by each intervention, while vaccine costs were assessed against robust estimates for the costs of mass drug administration obtained from data. We also calculated a critical vaccination cost, a cost beyond which vaccination might not be economically favorable, by benchmarking the cost-effectiveness of potential vaccines against the cost-effectiveness of mass drug administration, and examined the effect of different vaccine protection durations.ResultsWe found that sufficiently low-priced vaccines can be more cost-effective than traditional drugs in high prevalence settings, and can lead to a greater reduction in morbidity over shorter time-scales. MDA or vaccination programmes that target the whole community generate the most health benefits, but are generally less cost-effective than those targeting children, due to lower prevalence of schistosomiasis in adults.ConclusionsThe ultimate cost-effectiveness of vaccination will be highly dependent on multiple vaccine characteristics, such as the efficacy, cost, safety and duration of protection, as well as the subset of population targeted for vaccination. However, our results indicate that if a vaccine could be developed with reasonable characteristics and for a sufficiently low cost, then vaccination programmes can be a highly cost-effective method of controlling schistosomiasis in high-transmission areas. The population-level immunity generated by vaccination will also inevitably improve the chances of interrupting transmission of the disease, which is the long-term epidemiological goal.
Highlights
Schistosomiasis is a neglected tropical disease, targeted by the World Health Organization for reduction in morbidity by 2020
The ‘bounce-back’ effect, where recently treated hosts are rapidly reinfected, prevents large reductions in prevalence, despite years of repeated treatment. We contrast this with a vaccine that provides protection for ten years, delivered to children in cohorts; this generates a greater reduction in prevalence and heavy intensity prevalence in both school-aged children (SAC) and adults than mass drug administration (MDA) (Fig. 1c)
When SAC are vaccinated once every 5-years (Fig. 1d) there is a notable bounce-back after intervention, as unvaccinated pre-SAC children mature into the SAC group, but this is much slower than the bounce-back seen after a round of MDA
Summary
Schistosomiasis is a neglected tropical disease, targeted by the World Health Organization for reduction in morbidity by 2020. Schistosomiasis is estimated to affect over 250 million people, primarily in sub-Saharan Africa and South America It is caused by water-borne parasitic flukes from the genus Schistosoma (predominantly Schistosoma mansoni, Schistosoma haematobium and Schistosoma japonicum), which enter the body through the skin and colonize the host’s bloodstream. Substantial progress has been made recently in widening coverage, and schistosomiasis is on course to reach its WHO 2020 control target of treating 75% of SAC in endemic regions. Several recent studies in Africa have demonstrated limited progress in reducing prevalence in localized high-transmission areas, despite high MDA coverage [7,8,9]. Mathematical modelling suggests that high coverage of both children and adults over sustained periods of time is required for MDA to control schistosomiasis in high-transmission areas, which may prove to be beyond practical limits [10, 11]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
