Assessment of cost-effectiveness of universal hepatitis B immunization in a low-income country with intermediate endemicity using a Markov model

Transcription

1 Assessment of cost-effectiveness of universal hepatitis B immunization in a low-income country with intermediate endemicity using a Markov model Aggarwal R, Ghoshal U C, Naik S R 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 inclusion of a universal hepatitis B (HB) vaccine in a national immunisation programme of a low-income country, with intermediate HB endemicity, was studied. Universal HB vaccination consisted of three doses of vaccination in early life. Type of intervention Primary prevention. Economic study type Cost-effectiveness and cost-utility analyses. Study population The study population comprised a hypothetical cohort of newborn babies from low-income countries with intermediate HB endemicity. Setting The setting was primary care. The study was carried out in India. Dates to which data relate The effectiveness data were collected from studies published between 1986 and The cost data were obtained from studies published in 2000, and from experts' opinions. The price year appears to have been Source of effectiveness data The effectiveness data were derived from a non-systematic review of published studies and some authors' assumptions. Modelling A Markov model was used to estimate the health outcomes and costs associated with the introduction of the HB vaccine, compared with no introduction of the vaccine. The cycle length of the model was one year. The health benefits were estimated for a lifetime period, while the costs were estimated according to the period of vaccine administration. A cohort of 1,000 hypothetical newborns was considered to run the model. Outcomes assessed in the review The primary health outcomes assessed in the review were: the HB carrier rate in the absence of universal immunisation; Page: 1 / 6

2 the HB vaccine effectiveness rate; the HB vaccine coverage rate; the annual disease progression rates from chronic disease to compensated cirrhosis, from compensated cirrhosis to decompensated cirrhosis, from compensated cirrhosis to hepatocellular carcinoma, from decompensated cirrhosis to death, and from hepatocellular carcinoma to death; and the quality of life estimates for compensated cirrhosis, decompensated cirrhosis and hepatocellular carcinoma. These estimates were incorporated in the model as input parameters. Study designs and other criteria for inclusion in the review Sources searched to identify primary studies Criteria used to ensure the validity of primary studies Methods used to judge relevance and validity, and for extracting data Number of primary studies included At least 14 studies were included in the review. Most of these appear to have been observational studies. Methods of combining primary studies Investigation of differences between primary studies Since a meta-analysis was not carried out, no tests of homogeneity were performed. Results of the review The HB carrier rate in the absence of universal immunisation was 4% (range: ). The HB vaccine effectiveness rate was 95% (range: 70-99). The HB vaccine coverage rate was 75% (range: 40-95). The annual disease progression rate was: 1% (range: ) from chronic disease to compensated cirrhosis, 5% (range: ) from compensated cirrhosis to decompensated cirrhosis, 1% (range: ) from compensated cirrhosis to hepatocellular carcinoma, Page: 2 / 6

3 20% (range: 10-30) from decompensated cirrhosis to death, and 40% (range: 20-60) from hepatocellular carcinoma to death. The quality of life estimates were 0.82 (range: ) for compensated cirrhosis, 0.55 (range: ) for decompensated cirrhosis and 0.55 (range: ) for hepatocellular carcinoma. Methods used to derive estimates of effectiveness The authors made assumptions to derive some estimates of effectiveness. Estimates of effectiveness and key assumptions The authors assumed: the vaccine wastage rate was 20% (range: 5-30); the annual transition rates of progression from chronic HB to cirrhosis in the age groups 0-10 and were onetenth and one-half, respectively, of that among adults; all chronic HB infections occurred in the first year of life; and there was no mortality and or loss of quality-adjusted life-years (QALYs) due to acute and fulminant HB. Measure of benefits used in the economic analysis The model outcomes used in the economic analysis were the average number of life-years gained (LYG) and the average number of QALYs gained. The HB carrier rate associated with the HB immunisation strategy was also calculated. These outcomes were obtained from the Markov model. The authors stated that the utility weights applied to estimate the QALYs were obtained from clinician judgements published elsewhere. Direct costs The resource quantities and the costs were not reported separately. The direct costs considered in the economic analysis were those of the health service. These were for the vaccine and vaccine administration. The authors stated that the costs and impact of interferon or lamivudine treatment for HB, and screening for hepatocellular carcinoma were ignored. The direct costs were obtained from published studies and experts' assumptions. Therefore, the costs were estimated on the basis of both actual data and a guess. Discounting may not have been performed in the base-case analysis since the costs were incurred during a short time. The price year appears to have been Statistical analysis of costs No statistical analyses of the costs were performed. Indirect Costs No indirect costs were estimated. Currency US dollars ($). The conversion rate used was Indian Rupees 50 = $1. Sensitivity analysis One way-sensitivity analyses were performed to assess the robustness of the results when the values of the model parameters were varied. The ranges considered have been reported already (see the 'Results of the Review' section). Page: 3 / 6

4 The costs associated with the treatment of sequelae of chronic HB were considered in one of the sensitivity analyses. A discount rate of 3% was applied to this analysis. A threshold analysis was also performed to assess whether the costs of treating long-term complications of HB were the same for the HB-immunisation and the no immunisation strategies. Monte Carlo simulations were also used to consider probabilistic distributions of the model parameters, rather than fixed values. Therefore, the areas of uncertainty investigated were variability in the data and, as stated by the authors, applicability of the results. Estimated benefits used in the economic analysis The HB carrier rate with the introduction of the HB vaccine would be 1.15%. The number of LYG per child was for the non-immunised cohort versus for the immunised cohort. The incremental number of LYG gained per child in the immunised cohort, compared with the non-immunised cohort, was The number of QALYs per child was for the non-immunised cohort versus for the immunised cohort. The incremental number of QALYs gained per child in the immunised cohort, compared with the non-immunised cohort, was A lifetime period was considered when estimating these health benefits. Cost results The average costs per child were $0 in the non-immunised group versus $2.81 in the immunised group. Synthesis of costs and benefits The estimated health benefits and costs were combined through incremental cost-effectiveness ratios (ICERs), which calculated: the incremental cost per HB carrier prevented with the HB vaccination programme, compared with no HB immunisation ($98.60 per HB carrier prevented); the incremental cost per LYG with the HB vaccination programme, compared with no HB immunisation ($16.27 per LYG); and the incremental cost per QALY gained with the HB vaccination programme, compared with no HB immunisation ($13.22 per QALY gained). The sensitivity analyses showed that the study findings did not change considerably when the model parameters were varied. The highest ICERs were reached when the HB carrier rate was equal to 1%. This resulted in ICERs of $394.6 per HB carrier prevented, $65.06 per LYG and $52.89 per QALY gained with the HB vaccine, compared with no HB vaccination. HB vaccination was, therefore, the preferred strategy. Authors' conclusions The introduction of hepatitis B (HB) vaccination would lead to a reduction in the HB carrier rates, and gains in life expectancy and quality-adjusted life-years (QALYs), at a very reasonable cost. HB immunisation proved to be a highly cost-effective strategy when compared with no immunisation. CRD COMMENTARY - Selection of comparators A 'do nothing' alternative was considered as the comparator. This was appropriate since it was the current practice in the authors' setting, and it also allowed the estimation of the true effect of the introduction of the HB vaccine in their Page: 4 / 6

5 setting. You must consider the context in which this information is to be applied (a low-income country with intermediate HB endemicity), and whether HB immunisation is a strategy already implemented in your own setting. Validity of estimate of measure of effectiveness The authors did not state that a systematic review of the literature had been undertaken. A narrative method appears to have been used to combine the effectiveness estimates. The impact of differences between the primary studies was not considered when estimating the effectiveness. Moreover, some authors' assumptions were formulated, and not all of them were justified with reference to the medical literature. The fact that sensitivity analyses were performed, using appropriate ranges of variation for the effectiveness parameters, decreased the uncertainty surrounding the effectiveness results. Validity of estimate of measure of benefit The estimation of benefits was modelled using a Markov model, which seems to have been an appropriate instrument. The LYG and QALYs gained were reported to be the summary measures of benefit. These allow comparisons with results from other studies using the same type of measures. Validity of estimate of costs The resource quantities and the costs were not reported separately. Although the authors reported that a societal perspective was adopted, they did not include productivity losses associated with HB infection. The actual perspective adopted appears to have been that of the health service. The authors reported that the costs were estimated using a conservative approach. Therefore, if biases existed, these would be against the HB immunisation strategy and the results would still be valid. The results from the sensitivity analyses showed that the estimation of costs was very robust within the ranges of values considered at analysis. The price year appears to have been reported. It appears that discounting was not applied to the baseline analysis since the costs included here were those for vaccine administration, which were incurred over a short time. However, a discount rate was appropriately applied when the costs of long-term sequelae associated with HB infection were included in one of the sensitivity analyses. Other issues The authors made appropriate comparisons of their findings with those from other studies. They stated that, based on the robustness of the findings (as shown by the sensitivity analyses, which the authors stated covered differences that may exist between these countries), the results obtained in the present study are applicable to other low-income countries with intermediate HB endemicity. The scope of the analysis was reflected in the authors' conclusions. The authors discussed some limitations of their study. First, the model did not consider acute and fulminant disease due to HB. Second, the disease progression rates were derived from other geographical regions. Finally, the reliability of the cost data was unclear. However, the authors stated that, despite some limitations, their analysis overestimated the potential benefits and cost-effectiveness of the vaccination programme. Implications of the study The authors suggested that further research is needed to compare the cost-effectiveness of this preventive approach to HB with a therapeutic approach. Source of funding None stated. Bibliographic details Aggarwal R, Ghoshal U C, Naik S R. Assessment of cost-effectiveness of universal hepatitis B immunization in a lowincome country with intermediate endemicity using a Markov model. Journal of Hepatology 2003; 38(2): Page: 5 / 6

6 Powered by TCPDF ( PubMedID Other publications of related interest Ginsberg GM, Berger S, Shouval D. Cost-benefit analysis of a nation-wide inoculation programme against viral hepatitis B in an area of intermediate endemicity. Bulletin of the World Health Organization 1992;70: Miller MA, McCann L. Policy analysis of the use of hepatitis B. Haemophilus influenza type B-, Streptococcus pneumonia-conjugate and rotavirus vaccines in national immunization schedules. Health Economics 2000;9: Indexing Status Subject indexing assigned by NLM MeSH Cost-Benefit Analysis; Developing Countries /economics; Disease Progression; Endemic Diseases /economics /prevention & control; Health Care Costs /statistics & numerical data; Hepatitis B /economics /epidemiology /prevention & control; Hepatitis B Vaccines /economics; Humans; Immunization Programs /economics; India /epidemiology; Markov Chains; Models, Econometric; Monte Carlo Method; Poverty; Program Evaluation; Quality- Adjusted Life Years; Value of Life /economics AccessionNumber Date bibliographic record published 30/06/2004 Date abstract record published 30/06/2004 Page: 6 / 6