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Cost-effectiveness of novel vaccines for tuberculosis control: a decision analysis study |
Tseng CL, Oxlade O, Menzies D, Aspler A, Schwartzman K |
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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 assessed the cost-effectiveness of a hypothetical vaccine against tuberculosis, compared with the directly observed treatment, short course (DOTS) programme, and bacillus Calmette-Guerin vaccination coverage at the time, in a high-prevalence country. The authors concluded that the new vaccine, with moderate efficacy, plus a booster was most cost-effective. This vaccine produced cost savings and improved health outcomes, when added to existing control strategies. The cost-effectiveness methods were valid and the authors’ conclusions appear to be robust in most scenarios. Type of economic evaluation Cost-effectiveness analysis Study objective This study assessed the cost-effectiveness of a hypothetical vaccine against tuberculosis (TB), compared with the usual strategy of directly observed treatment, short course (DOTS), with the bacillus Calmette-Guerin (BCG) vaccination coverage at the time, in a high-prevalence country. Interventions The usual care consisted of a BCG vaccination for newborns, plus the DOTS strategy, which included sputum smear diagnosis for those with symptoms and standard drug treatments. The two hypothetical vaccine, population strategies were vaccination with a new more effective vaccine at birth, and vaccination with this new vaccine at birth plus a booster at 10 years old. Methods
Analytical approach:The analysis was based on a decision model, followed by a Markov process, with a time horizon of 30 years. The authors stated that it was carried out from the perspective of society.
Effectiveness data:The clinical data were from a selection of relevant studies. Some epidemiological estimates were from Zambian databases while other estimates were from published sources. A number of assumptions were made for the hypothetical vaccine's efficacy and duration of efficacy, which were key inputs for the simulation. It was assumed that there was no herd immunity.
Monetary benefit and utility valuations:Not considered.
Measure of benefit:The summary benefit measures were the number of active cases of TB and the deaths due to TB. A 3% annual discount rate was applied.
Cost data:The economic analysis included the direct and indirect costs. The direct costs were those borne by the government and the health care system, plus those for the implementation and maintenance of the programme. The indirect costs included out-of-pocket expenses for patients and families, and lost productivity due to disability or death from TB. The resource consumption was from Zambian sources, and the costs were from other countries, with comparable national incomes, or from official national sources. The hypothetical vaccine costs were based on a survey and assumptions. The costs of research, development, and production of the vaccine were from a World Health Organization (WHO) report. All costs were in US dollars ($) and were discounted at an annual rate of 3%. The price year was 2007.
Analysis of uncertainty:One-way sensitivity analyses were carried out to examine if the model outcomes were robust to variations in the key epidemiological inputs, costs, discount rate, vaccine efficacy, and the prevention of acquisition of TB and the prevention of late reactivation, as alternative outcomes for the vaccine. Results Over 30 years, usual care resulted in 25,557 active TB cases and 18,379 TB deaths, in 468,073 Zambians born in the first year of the simulation. The direct costs were $11.4 million and the indirect costs were $45.1 million.
Compared with this, the new vaccine, with 70% efficacy against rapid progression to TB disease, prevented 932 active TB cases and 422 TB deaths. This saved $0.2 million in direct costs and $3.4 million in indirect costs; a total of $3.6 million societal costs saved.
The addition of the booster, averted 931 TB cases and 589 TB deaths, compared with one neonatal dose of the new vaccine. This increased the direct costs by $0.6 million and reduced the indirect costs by $6.2 million, compared with usual care; resulting in a net societal saving of $2.0 million, compared with the one dose of the new vaccine.
The cost savings started one year after vaccination for the new vaccine at birth only, and five years after initial vaccination for the booster strategy, due to higher initial development costs. Cost savings were predicted even if the initial development costs or the vaccine costs were quadrupled.
The base-case results were robust when varying the epidemiological inputs and when vaccine efficacy was reduced to 60%. The two new vaccine strategies did not save costs only in the worst-case scenario, in which all the inputs favoured usual care. The duration of vaccine efficacy had an impact on the cost-effectiveness of these two strategies. Authors' conclusions The authors concluded that a vaccination and booster, using a new TB vaccine with moderate efficacy, was most cost-effective. The improved vaccine produced considerable cost savings and favourable health outcomes, when added to existing control strategies. CRD commentary
Interventions:The selection of the comparators appears to have been appropriate. It included the usual care in Zambia and two strategies based on a vaccine that had not been developed at the time.
Effectiveness/benefits:The clinical evidence was from a selection of relevant sources, but no systematic review was reported. Limited information on the methods of these studies was provided, reducing the possibility of assessing their validity. The authors selected data from countries with comparable sociodemographics, or from WHO publications, if evidence from Zambia was not available. The vaccine efficacy and its duration were assumed, as it had not been developed. The uncertainty in these values was assessed in the sensitivity analysis. The assumption of no herd immunity was conservative against the new vaccine. The benefit measures captured the impact of the disease on patients’ health, but will be difficult to compare with the benefits of other health care interventions, as they were disease-specific.
Costs:A broad perspective was adopted and appropriate costs appear to have been included. A full list of cost items was not provided; total categories were presented. Some unit costs and resource quantities were reported, as were the data sources, but these were not extensively described. The authors used data from similar countries, where data from Zambia were not available, which appears to have been reasonable. The price year and discounting were clearly stated. The impact of alternative cost estimates was tested in the sensitivity analyses.
Analysis and results:The results were extensively presented. A synthesis of the costs and benefits was not required as the new vaccine strategies were economically and clinically superior. The uncertainty was partly considered in deterministic analyses and alternative scenarios. A more comprehensive assessment, with inputs varied simultaneously, would have been helpful. The authors acknowledged some limitations to their analysis, mainly due to the lack of cost data for vaccine development and production in Zambia and the lack of efficacy data. It was assumed that there were no adverse events with the vaccine and this assumption was not tested in the sensitivity analysis. The societal perspective was good, as it incorporated all the relevant costs. The analysis appears to have been specific to countries with a high TB incidence and a low income.
Concluding remarks:The cost-effectiveness methods were valid and the authors’ conclusions appear to be robust in most scenarios. Funding Support received from the McGill University Faculty of Medicine, the Canadian Institutes of Health Research, and the Fonds de la Recherche en Sante du Quebec. Bibliographic details Tseng CL, Oxlade O, Menzies D, Aspler A, Schwartzman K. Cost-effectiveness of novel vaccines for tuberculosis control: a decision analysis study. BMC Public Health 2011; 11:55 Indexing Status Subject indexing assigned by NLM MeSH Adolescent; Adult; BCG Vaccine /economics /therapeutic use; Child; Child, Preschool; Communicable Disease Control /economics; Cost of Illness; Cost-Benefit Analysis; Decision Support Techniques; Directly Observed Therapy; Health Care Costs /statistics & Health Expenditures /statistics & Humans; Infant; Infant, Newborn; Mycobacterium tuberculosis /drug effects; Tuberculosis /economics /prevention & Tuberculosis Vaccines /economics /therapeutic use; Young Adult; Zambia; control; numerical data; numerical data AccessionNumber 22011001207 Date bibliographic record published 24/08/2011 Date abstract record published 26/01/2012 |
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