|
Cost-effectiveness of hepatitis A immunization of children and adolescents in Germany |
Diel R, Rappenhoner B, Schneider S |
|
|
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 implementation of an immunisation strategy against hepatitis A virus (HAV) infection was studied. Two different strategies were compared:
mass immunisation of 1-year-old children using Vaqta pro infantibus, in order to prevent the infection as soon as possible; and
immunisation of all adolescents aged 11 to 15 years, (in the same way as hepatitis B immunisation).
Economic study type Cost-effectiveness analysis.
Study population The study based its disease projections on the general German population.
Setting The setting was community care. The economic study was carried out in Germany.
Dates to which data relate The model parameters were collected from studies published between 1985 and 1999. The costs appeared to be related to 1997, 1998 and 2000. The price years may have been 1998 for most of the costs, and 2000 for the costs of the vaccine for the children.
Source of effectiveness data The effectiveness data were obtained from a review of completed studies.
Modelling A dynamic model, using an iterative process, was used to model both the effectiveness and costs of each of the strategies for HAV immunisation under study. A 30-year study period (from 1998 until 2029) was studied. This was divided into 3 cycles of 10 years. The costs and effectiveness were modelled for individuals up to a maximum of 44 years. The population at risk was recalculated every year considering that those infected individuals would gain permanent immunity. The model took account of age cohort sizes, demographic changes and migratory movements.
Outcomes assessed in the review The model outcomes assessed in the review were:
the vaccine effectiveness;
the compliance rate for individuals aged under 11 years, and 11 or older;
the symptomatic disease rate for individuals under 15 years, and 15 or older;
the infection rates for individuals between 15 and 44 years; and
the incidence rates by age groups and the overall incidence rate. The age groups were less than 1 year old, between 1 and 4 years, between 5 and 14 years, between 15 and 24 years, between 25 and 44 years, between 45 and 64 years, and 65 years or older.
For the long-distance travellers, the health outcomes assessed were the immunisation rates, the number of long-distance travellers, the attack rate and the secondary infection rate.
Study designs and other criteria for inclusion in the review It does not appear that a systematic review has been conducted. No inclusion or exclusion criteria were reported.
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 18 published studies were included in the review.
Methods of combining primary studies It appears that the model parameters were selected from specific studies most appropriate to the model.
Investigation of differences between primary studies Results of the review The vaccine effectiveness was 99%.
The compliance rate was 80% among those younger than 11 years, and 20% for those aged 11 years or older.
The symptomatic disease rate was 10% for those younger than 15 years, and 75% for those aged 15 years or older.
The infection rate was 7% for those aged 15 years or older.
The incidence rates by age groups were as follows:
2.0% for less than 1 year old;
8.7% for those aged from 1 to 4 years;
9.4% for those aged from 5 to 14 years;
5.9% for those aged from 15 to 24 years;
5.5% for those aged from 25 to 44 years;
2.3% from those aged 45 to 64 years; and
1.2% for those aged 65 years or older.
The overall incidence rate was 4.7%.
For the long-distance travellers:
the immunisation rate was 10% (this was deemed the worst-case scenario);
5,440,000 travellers were considered at the starting point;
the attack rate was 3.6%; and
the secondary infection rate was 10%.
Methods used to derive estimates of effectiveness The authors made a key assumption.
Estimates of effectiveness and key assumptions The authors assumed that, at the beginning of the period, there was a negligibly low infection rate (0%) for those under 15 years, and an increase of 1% per year was generated in the age group 15 to 44 years.
Measure of benefits used in the economic analysis The summary measure of benefit used in the economic analysis was the number of cases of HAV infection avoided. This was derived by modelling, using a temporal horizon of 30 years (3 cycles of 10 years each cycle). Discounting was performed using a 5% discount rate.
Direct costs Some of the resource quantities were reported separately from the costs. The direct costs considered in the economic analysis seemed to be those of the health service, namely immunisation (i.e. costs of the vaccine and vaccine administration) and treatment. The treatment costs included both outpatient and inpatient costs, depending on the severity of the disease. Charges were reported in some instances and it is uncertain if these equalled the true costs of the resource items. The costs quoted were average costs. The cost data were obtained from one published study and the Medicines Supply Contract between the Association of Employees Health Insurers and the Association of Workers' Substitute Funds (VdAK/AEV). Therefore, the cost estimates were derived using actual data. A dynamic model was used to estimate the incremental costs during the 30-year period for the two mass immunisation strategies, compared with the private immunisation strategy for long-distance travellers. Discounting was performed using a 5% discount rate. This was appropriate since the time period considered for the economic analysis was longer than 2 years. The price year was not stated, although it appears that different costs have been reported for different years. For example, the inpatient treatment costs were reported for 1998, while the costs of the vaccine for 1-year-old children were reported for 2000.
Statistical analysis of costs The costs were treated deterministically.
Indirect Costs The indirect costs were included to take account of lost productivity due to HAV infection. The frequency of infection across different regions, the number of cases and the average lost working time were reported separately from the wage per employee. The indirect costs came from a published study and, therefore, were derived from actual data. Discounting was performed using a 5% discount rate. This was appropriate since the period of analysis was longer than 2 years. The price year was 1998.
Sensitivity analysis One-way sensitivity analyses were performed in order to assess the robustness of the model to variations in some of the parameters. The effectiveness estimators varied were compliance (90% for individuals younger than 11 years and 50% for those aged at least 11 years), the symptomatic disease among those younger than 15 years (30%), the immunisation rate among long-distance travellers (30%), and the number of long-distance travellers (assuming an increase of 10%). The immunisation costs were also increased and decreased by 10%, and the per-case costs were increased by 10%. The area of uncertainty investigated was, therefore, variability in the data. A 3% discount rate was also applied.
Estimated benefits used in the economic analysis Compared with the private immunisation of long-distance travellers aged between 15 and 44 years, the number of cases of HAV infection avoided by the mass immunisation strategy of 1-year-old children was 6,266 (first decade), 18,049 (second decade), 24,298 (third decade) and 48,613 (whole study period).
Compared with the private immunisation of long-distance travellers aged between 15 and 44 years, the number of cases of HAV infection avoided by the mass immunisation strategy of adolescents aged between 11 and 15 years was 2,313 (first decade), 6,428 (second decade), 8,575 (third decade) and 17,316 (whole study period).
The benefits were estimated for a period of 3 cycles, with 10 years per cycle (30 years in total). The estimated benefits were discounted using a 3% discount rate.
Cost results The following was inferred from the text since the tables did not adequately define their contents. The discounted incremental costs of the mass immunisation strategy of 1-year-old children, compared with the private immunisation of long-distance travellers aged between 15 and 44 years, were DM 534.01 million (first decade), DM 808.02 million (second decade) and DM 1,236.97 million (third decade).
The discounted incremental costs of the mass immunisation strategy of adolescents between 11 and 15 years, compared with the private immunisation of long-distance travellers aged between 15 and 44 years, were DM 428.48 million (first decade), DM 393.97 million (second decade) and DM 619.05 million (third decade).
Synthesis of costs and benefits The incremental cost-effectiveness ratios (ICERs) were calculated as the ratio between the discounted incremental costs over the discounted cases of HAV avoided for both mass immunisation strategies, in comparison with the private immunisation strategy of long-distance travellers. Ideally, one should report the ICERs of one strategy compared to the next most effective. These ICERs were reported for each of the decades considered at analysis, and for the overall study period.
Compared with the private immunisation of long-distance travellers aged between 15 and 44 years, the ICERs for the mass immunisation strategy of 1-year-old children were DM 85,223 (first decade), DM 44,768 (second decade), DM 50,908 (third decade) and DM 53,052 (overall study period) per case avoided.
Compared with the private immunisation of long-distance travellers aged between 15 and 44 years, the ICERs for the mass immunisation strategy of adolescents between 11 and 15 years were DM 185,249 (first decade), DM 61,290 (second decade), DM 72,192 (third decade) and DM 83,247 (overall study period) per case avoided.
The authors reported that the most sensitive parameter under the mass immunisation strategy of 1-year-old children was the travel immunisation rate. This reduced the number of cases of infection by about 80% when a rate of 30% was considered. The ICER of the mass immunisation strategy of adolescents between 11 and 15 years old was also very sensitive to changes in the rate of travel immunisation. The ICER increased to DM 106,056 per case of HAV infection avoided during the overall study period when a rate of 30% was considered. On the other hand, a decrease in the discount rate to 3% considerably improved this CER, which was DM 53,708 per case of HAV infection avoided for the overall study period.
Authors' conclusions The incremental benefit of an additional mass immunisation strategy for 1-year-old children, or for adolescents between 11 and 15 years, is relatively small and not cost-effective.
CRD COMMENTARY - Selection of comparators The comparator chosen was justified on the grounds that the immunisation of long-distance travellers aged between 15 and 44 years, under private preventive health care, was the current practice in the authors' setting. You should decide if the strategies compared are appropriate for your use.
Validity of estimate of measure of effectiveness The authors did not report that a systematic review was undertaken. Instead, the effectiveness analysis was based on statistical population data and some effectiveness studies. Some estimates were derived from a single source. It was not stated how the estimates were derived from multiple studies. Sensitivity analyses were performed on some effectiveness estimates, in order to assess the robustness of the results to variations in the effectiveness data. The authors focused on investigating the effectiveness results under a better scenario in comparison with the base-case analysis. However, a worst-effectiveness scenario was not considered.
One of the effectiveness assumptions used in the model was that, at the beginning of the period, there was a negligibly low infection rate (0%) for those under 15 years, and an increase of 1% per year was generated in the age group of 15 to 44 years. This assumption does not seem consistent with the authors' statement relating to the high incidence of infection among children aged less than 15 years.
Validity of estimate of measure of benefit The estimation of benefits was modelled using a dynamic model, which appears to have been appropriate.
Validity of estimate of costs The perspective adopted was societal, and both the direct and indirect costs were appropriately included. Patient costs should have been considered for a fully societal perspective. Some of the resource quantities were reported separately from the costs. Reimbursement prices were reported for the vaccines and also some charges, which may not reflect opportunity costs. Some one-way sensitivity analyses on the costs were performed. Several different years for the prices were reported. The authors did not state whether the costs were adjusted to a common year. These facts introduce uncertainty into the reliability of the conclusions. They also hinder reflation exercises and the generalisation of the results to other settings. The authors reported that the model assumptions may have underestimated the CERs because they did not take account of booster injections and the immunisation of occupationally exposed groups of people, and ring vaccination in communal establishments and residential accommodation.
Other issues The authors only calculated the ICERs for each intervention in comparison with the private insurance alternative. It would have been better had they calculated the ICERs of each strategy in relation to the next most effective strategy, having eliminated dominant strategies. The authors compared the results for the incidence rates of HAV infection with those from official reports. These results turned out to be very similar to those of the official reports, thereby, as the authors stated, validating the use of the chosen model. The issue of the generalisability of the results to other settings was not discussed. However, some sensitivity analyses help in this regard. While the results were reported in full, the labelling of the tables could have been better. The authors' conclusions reflected the scope of the analysis.
Implications of the study The authors highlighted the fact that the study took account of the indirect secondary effects of an immunisation programme. Therefore, the number of cases avoided by an immunisation strategy was not overestimated. The authors consider that the statutory health insurance should not bear the costs of any additional mass immunisation strategy.
Bibliographic details Diel R, Rappenhoner B, Schneider S. Cost-effectiveness of hepatitis A immunization of children and adolescents in Germany. Health Economics in Prevention and Care 2001; 2: 96-103 Other publications of related interest Arnal JM, Frisas O, Garuz R, Antonanzas F. Cost-effectiveness of hepatitis A virus immunisation in Spain. Pharmacoeconomics 1997;12:361.
Behrens RH, Roberts JA. Is travel prophylaxis worth while? Economic appraisal of prophylactic measures against malaria, hepatitis A, and typhoid in travellers. BMJ 1994;309:918.
Das A. An economic analysis of different strategies of immunisation against hepatitis A virus in developed countries. Hepatology 1999;29:548.
O'Connor JB, Imperiale TF, Singer ME. Cost-effectiveness analysis of hepatitis A vaccination strategies for adults. Hepatology 1999;30:1077.
Severo CA, Fagnani F, Lafuma A. Cost effectiveness of hepatitis A prevention in France. Pharmacoeconomics 1995;8:46.
Indexing Status Subject indexing assigned by CRD MeSH Adolescent; Age Factors; Cost-Benefit Analysis; Female; Germany /epidemiology; Hepatitis A /epidemiology /prevention & Hepatitis A Vaccines /therapeutic use /economics; Humans; Immunization /economics; Infant; Male; control AccessionNumber 22001008251 Date bibliographic record published 30/09/2003 Date abstract record published 30/09/2003 |
|
|
|