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The cost-effectiveness of universal vaccination of children against hepatitis A in Argentina: results of a dynamic health-economic analysis |
Lopez E, Debbag R, Coudeville L, Baron-Papillon F, Armoni J |
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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. Health technology The study examined a universal vaccination programme against hepatitis A in toddlers (between 1 year and school age). The vaccination involved the recommended two-dose schedule administered at age 12 and 18 months.
Type of intervention Primary prevention (vaccination).
Economic study type Cost-effectiveness analysis.
Study population The study population comprised a hypothetical cohort of toddlers (between 1 year and school age).
Setting The setting was primary care. The economic study was carried out in Argentina.
Dates to which data relate The clinical data were derived from studies published between 1999 and 2006. The resource use and cost data were presumably derived from a study published in 2004. The price year was not reported.
Source of effectiveness data The clinical data used to populate the decision model were:
the size of the birth cohort,
disease outcomes per symptomatic cases (hospitalisations, fulminant hepatic failure, liver transplantation and re-transplantation, and relapses),
the age-specific hepatitis A fatality rates, and
vaccine characteristics (seroconversion rates, adverse events and annual rate of waning of seroprotection).
Modelling The decision model took not only the epidemiological change in the level of endemic hepatitis into account, but also the direct and indirect (i.e. vaccine-induced herd immunity) effects of vaccination. The time horizon of the model was 100 years. The model was used to obtain the number of cases of symptomatic and fatal infections, as well as to evaluate the impact of vaccination on the number of life-years (LYs) lost because of hepatitis A. Health states and algorithms for time-dependent transition probabilities were reported.
Sources searched to identify primary studies Demographic data were derived from the World Health Organization and the Argentine National Institute of Statistics and Censuses. Much of the data on disease outcomes came from a retrospective survey of patients with hepatitis A admitted to an Argentinean hospital between November 1992 and June 2003. The sources of the other data were not described.
Methods used to judge relevance and validity, and for extracting data The primary studies might have been identified selectively as details of a systematic review of the literature were not reported. The authors used epidemiological and clinical real-life data from Argentina, wherever possible, to make the model representative of the study context.
Measure of benefits used in the economic analysis The summary benefit measure used was the expected number of LYs gained by a reduction in the levels of asymptomatic and symptomatic hepatitis A infection. The LYs gained were estimated using the decision model. The reduction in the number of hepatitis A infections, symptomatic cases, and deaths were also reported, although they were not combined with the costs. The LYs gained were discounted at a rate of 3%, which was appropriate given the long-term time horizon.
Direct costs The categories in the cost analysis included laboratory tests, immunoglobulin M administration, outpatient medical visits, hospitalisations, fulminant hepatic failure with or without liver transplantation, re-transplantation of the liver, and vaccine acquisition and administration. The unit costs were presented only for some items, whereas the quantities of resources used were not given. The costs were derived from a childhood vaccination programme against hepatitis A in Argentina, although details on the source of these data were not given. Discounting was relevant, as the long-term costs were evaluated, and an annual rate of 3% was used. The price year was not explicitly reported.
Statistical analysis of costs The costs were treated deterministically.
Indirect Costs The indirect costs were included in the analysis and were calculated, but no details of the sources or methods used to obtain these costs were provided. A discount rate of 3% was presumably applied to the productivity costs.
Currency US dollars ($). Argentine pesos (ARS) were converted into US dollars at the exchange rate of $1 = ARS 3, as per the year 2004.
Sensitivity analysis A range of univariate sensitivity analyses were carried out to assess the robustness of the cost-effectiveness ratios to variations in vaccination coverage, annual reductions in the force of infection, time horizon, discount rate, levels of herd immunity, and disease costs. The authors presumably set the alternative values investigated.
Estimated benefits used in the economic analysis In the base-case analysis, with a 95% coverage rate, a 1% decrease in force of infection and a 100-year time horizon, 652,153 children would be vaccinated in Argentina. This would reduce the number of hepatitis A infections from 380,278 to 27,873 (difference 352,405) and avoid a total of 121,587 symptomatic cases and 428 deaths (reduction of 90.7% and 90.3% of cases, respectively).
The number of LYs lost would be 8,701 with no vaccination versus only 1,704 with vaccination. Thus, the vaccination programme would prevent the loss of 6,997 LYs.
With 70% coverage, the number of symptomatic cases would be reduced by 90.7% and the number of deaths by 70.7%.
Cost results In the base-case analysis, the total cost was $17,605,176 with vaccination versus $41,595,140 with no vaccination. Thus, the vaccination strategy led to cost-savings of $23,989,963 over no vaccination.
The extra cost of vaccine (less then $9.5 million) was more than offset by a reduction in other direct costs (more than $20 million) and indirect costs (more than $12 million).
Synthesis of costs and benefits The costs and benefits were combined in an incremental cost-effectiveness ratio, but this is not informative as the vaccination strategy was more effective and less expensive than the no vaccination option. The programme would be dominant even after 10 years.
The sensitivity analysis revealed that vaccination remained largely dominant in all scenarios considered. The break-even price per dose of hepatitis A vaccine (the point at which the cost of the vaccination programme and the disease are equivalent) was $25, more than three times the current price ($7).
Authors' conclusions The routine vaccination of toddlers against hepatitis A in Argentina reduced symptomatic cases and deaths and was cost-saving from a societal perspective.
CRD COMMENTARY - Selection of comparators The rationale for the choice of the comparators was clear. No vaccination represented the conventional pattern of care before the implementation of the vaccination programme. The vaccination of specific groups of patients was not considered. You should decide whether they are valid comparators in your own setting.
Validity of estimate of measure of effectiveness The effectiveness data might have been identified selectively as the authors did not describe a systematic review of the literature. The sources of data referred to the Argentine context, whenever possible, in order to be representative of the epidemiological context of the study. However, limited information on the other primary studies was provided. Given the uncertainty surrounding some parameters, the impact of variations in key epidemiological inputs was investigated in the sensitivity analysis. Validity of estimate of measure of benefit Survival was an appropriate benefit measure as it represents the key output of a vaccination model. Discounting was performed, in accordance with international guidelines. The use of a decision model enabled the impact of herd immunity on expected survival to be evaluated.
Validity of estimate of costs The analysis of the costs was consistent with the perspective of the study, although the inclusion of productivity costs was unclear. The economic impact of mortality was evaluated, but the authors did not provide a clear explanation of the micro-categories of costs included in the analysis. In addition, only macro-categories were presented for the direct costs. Statistical analyses of the costs were not performed, but the impact of variations in disease costs was investigated in the sensitivity analysis. The price year was not reported, which will hinder reflation exercises in other settings. The analysis revealed that the vaccination programme is likely to remain cost-saving, even if the price of vaccination increases substantially.
Other issues The authors stated that their findings compared favourably with those from other studies, especially with a similar modelling study that was carried out in Israel. The issue of the generalisability of the study results to other settings was not explicitly addressed. However, epidemiological, clinical and cost data were varied in sensitivity analyses, and the results were robust to changes in these parameters. The study referred to the general population of toddlers and this was reflected in the authors' conclusions.
Implications of the study The study results support the decision taken in 2005 by the Argentine government to implement routine vaccination of toddlers against hepatitis A.
Bibliographic details Lopez E, Debbag R, Coudeville L, Baron-Papillon F, Armoni J. The cost-effectiveness of universal vaccination of children against hepatitis A in Argentina: results of a dynamic health-economic analysis. Journal of Gastroenterology 2007; 42(2): 152-160 Other publications of related interest Because readers are likely to encounter and assess individual publications, NHS EED abstracts reflect the original publication as it is written, as a stand-alone paper. Where NHS EED abstractors are able to identify positively that a publication is significantly linked to or informed by other publications, these will be referenced in the text of the abstract and their bibliographic details recorded here for information.
Ginsberg GM, Slater PE, Shouvar D. Cost-benefit analysis of a nationwide infant immunization programme against hepatitis A in an area of intermediate endemicity. J Hepatol 2001;34:92-9.
Armstrong GL, Bell BP. Hepatitis A virus infections in the United States: model-based estimates and implications for childhood immunization. Pediatrics 2002;109:839-45.
Demicheli V, Carniglia E, Fucci S. The use of hepatitis A vaccination in Italy: an economic evaluation. Vaccine 2003;21:2250-7.
Arnal JM, Frisas O, Garuz R, Antonanzas F. Cost-effectiveness of hepatitis A virus immunisation virus in developed countries. Pharmacoeconomics 1997;12:361-73.
Indexing Status Subject indexing assigned by NLM MeSH Argentina; Child, Preschool; Cost-Benefit Analysis; Hepatitis A /prevention & Hepatitis A Vaccines /economics; Humans; Infant; control AccessionNumber 22007000618 Date bibliographic record published 31/08/2007 Date abstract record published 31/08/2007 |
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