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Economic impact of dengue illness and the cost-effectiveness of future vaccination programs in Singapore |
Carrasco LR, Lee LK, Lee VJ, Ooi EE, Shepard DS, Thein TL, Gan V, Cook AR, Lye D, Ng LC, Leo YS |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. CRD summary This study examined the cost-effectiveness of a possible mass campaign of vaccination against dengue in a high-resource tropical country. The authors concluded that dengue vaccination reduced the economic and disease burden, and was likely to be cost-effective at reasonably low vaccine prices, in Singapore. The study had transparent and appropriate methods, which enhances the validity of the authors’ conclusions. Type of economic evaluation Study objective This study examined the cost-effectiveness of a mass campaign of vaccination against dengue, in a high-resource country. Interventions The mass vaccination campaign used two or three doses and was compared with the usual Vector Control programme, consisting of five strategies to prevent or control the disease. Vaccination was assumed to be given at random to a proportion of the population. Methods Analytical approach:An analytic framework was used to estimate the economic and health burden of dengue, and the subsequent impact of a national vaccination programme. The time horizon was 75 years. The authors did not explicitly state the perspective. Effectiveness data:The clinical data were from various sources, including surveillance databases, administrative sources, published studies, and assumptions. Two key sources of evidence were the Early Dengue (EDEN) Infection and Outcomes study of 455 individuals with fever of unknown cause, and the Adult Retrospective Dengue Study at Tan Tock Seng Hospital (ARDENT), which reported the characteristics of dengue patients from 2004 to 2008. Expansion factors were used for missing data for both in-patient and out-patient cases. Seroconversion rates were assumed, where they were not available from published sources. Vaccine efficacy, which was the key clinical input, was assumed by the authors and varied with waning and herd protection. Monetary benefit and utility valuations:The disability weights were estimated using data from the literature, World Health Organization (WHO) disability weights, and data from an empirical study that measured the daily losses in quality of life throughout an infection, using a visual thermometer scale. Measure of benefit:Disability-adjusted life-years (QALYs) were the summary benefit measure and they were discounted at an annual rate of 3%. Cost data:The economic analysis included direct medical and non-medical costs, and indirect costs. Hospital costs were from hospital bills provided by public hospitals in Singapore in 2010. Out-patient costs included consultation fees, tests, and treatment and were based on official tariffs. Non-medical costs included individual and family transport, and control costs, which were from the National Environment Agency (NEA). Indirect costs included reduction in work productivity, reduction in household services, loss of schooling, and increased need for care. Work productivity losses were estimated using two methods: the human-capital approach and the friction-cost method. Other costs were based on official tariffs, or were from the ARDENT project, the EDEN study or other sources. The cost of vaccination was uncertain as the vaccine had not been developed, so instead of assuming a single price, the authors estimated the threshold price above which vaccination would not be cost-effective. Costs were in US $ and the reference year was 2010. Where required, a 3% annual discount rate was applied. Analysis of uncertainty:Alternative assumptions for selected parameters were considered, based on published data or authors’ opinions. All parameters were increased by 30% in univariate sensitivity analyses. Results Depending on the scenario, the total costs ranged from $0.35 to $0.65 billion without control and from $85 to $1.15 billion with control. The total disease burden ranged from 5.8 to 27.4 DALYs per 100,000 individuals. The threshold price per dose, beyond which vaccination was no longer cost-effective, compared with the Vector Control programme, ranged from $53 for vaccination in three doses producing 10 years of immunity to $287 for two doses producing lifetime immunity. The threshold price beyond which vaccination was no longer cost-effective, at a cost-effectiveness threshold of three times the gross domestic product of Singapore per person, ranged from $95 per dose for three doses lasting 10 years, to $491 per dose for two doses lasting a lifetime. The most influential inputs for the health burden were the duration of symptoms for dengue haemorrhagic fever, the disability weight for dengue fever, and proportion of dengue haemorrhagic fever cases. The most influential inputs for the total costs were the assumptions used to calculate hospitalised cases, the hospitalisation cost per day, and the length of hospital stay. Authors' conclusions The authors concluded that dengue vaccination reduced the economic and disease burden, and was likely to be cost-effective at reasonably low vaccine prices, in Singapore. CRD commentary Interventions:The selection of the comparators was appropriate for the setting and for other tropical countries. Effectiveness/benefits:The clinical data were from several sources, selected by the authors; these were generally representative of the Singapore setting and were appropriate for estimating the burden of disease in Singapore. No data were available for vaccine efficacy, so some assumptions had to be made and these were varied in the sensitivity analyses. This was a potential drawback of the study. Little information was provided on the other data sources. DALYs were an appropriate benefit measure for capturing the impact of the disease on quality of life and survival. Details of the calculation of the disability weights were reported and appropriate alternative approaches were investigated. Costs:The economic analysis was satisfactorily carried out. A breakdown of cost items was reported. The authors did not explicitly state the perspective of the analysis, but the wide range of costs included suggests a societal viewpoint. Two methods were appropriately used to estimate the productivity losses, as recommended by the WHO, resulting in conventional estimates and more conservative ones. The unit costs, quantities of resources, and data sources were clearly reported. The price year was clearly stated, allowing reflation exercises. Analysis and results:The study results were only presented in graphs. An incremental approach was used to synthesise the costs and benefits of the strategies. Several relevant scenarios were considered, given the hypothetical nature of the vaccination programme. Influential inputs were identified by a deterministic sensitivity analysis. The authors acknowledged that the main limitation of their analysis was the lack of data for vaccine efficacy, which required various assumptions and scenarios. The study results might be relevant to other countries with similar epidemiology and economics. Concluding remarks:The study had transparent and appropriate methods, which enhances the validity of the authors’ conclusions. Funding Funding received from the National University of Singapore, and the National Medical Research Council, Singapore. Bibliographic details Carrasco LR, Lee LK, Lee VJ, Ooi EE, Shepard DS, Thein TL, Gan V, Cook AR, Lye D, Ng LC, Leo YS. Economic impact of dengue illness and the cost-effectiveness of future vaccination programs in Singapore. PLOS Neglected Tropical Diseases 2011; 5(12): e1426 Indexing Status Subject indexing assigned by NLM MeSH Adolescent; Adult; Aged; Aged, 80 and over; Child; Child, Preschool; Cost-Benefit Analysis; Dengue /economics /epidemiology /prevention & Dengue Vaccines /administration & Female; Humans; Infant; Infant, Newborn; Male; Middle Aged; Singapore /epidemiology; Vaccination /economics; Young Adult; control; dosage /economics /immunology AccessionNumber 22012001555 Date bibliographic record published 16/03/2012 Date abstract record published 19/02/2013 |
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