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Cost-benefit analysis of active vaccination campaigns against hepatitis A among daycare centre personnel in Israel |
Chodick G, Lerman Y, Peled T, Aloni H, Ashkenazi S |
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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 Mass and selective active vaccination campaigns against hepatitis A were compared. In addition, these strategies were compared with the use of nonspecific immune globulin for the prevention of the disease among daycare centre employees in Israel.
Study population The study population consisted of daycare centre and kindergarten workers currently employed in Israel.
Setting The setting was the community (workplaces). The sample was taken from daycare centres and kindergartens in Israel.
Dates to which data relate The range of publication years for the various sources of cost and effectiveness data used in this analysis was not clearly stated. 2000 prices were used.
Source of effectiveness data The source of effectiveness data was a synthesis of completed studies and other sources of relevant data.
Modelling A Markov model was used to estimate benefits and costs.
Outcomes assessed in the review The outcomes employed in the study included the incidence rate of hepatitis A, immunity to hepatitis A virus, case fatality rate, and relapse rate.
Study designs and other criteria for inclusion in the review The authors specified no exclusion/inclusion criteria. Most of the epidemiological data were taken from two studies previously carried out by the authors, one of which was an historical prospective study.
Sources searched to identify primary studies The authors did not specify sources searched to identify primary studies. There does not appear to have been any systematic extraction of primary studies.
Criteria used to ensure the validity of primary studies No criteria were mentioned.
Methods used to judge relevance and validity, and for extracting data Most of the data were extracted from two previous studies carried out by the same authors. The authors did not state why data were not extracted from more studies.
Number of primary studies included Data were taken primarily from two studies carried out by the authors. Some effectiveness data were also taken from seven other studies but no details were given about what type of studies these are.
Methods of combining primary studies Values of the probabilities used were inserted into a Markov model.
Investigation of differences between primary studies It does not appear that the authors investigated any differences between the primary studies or what effects these would have on the estimates of effectiveness.
Results of the review Over the next two decades, more than 1,200 cases of hepatitis A are expected, of which at least eight cases will be fatal, out of a population of less than 40,000 workers. More than 75% of the expected cases are workers currently under 40 years of age. The model predicts a gradual decrease in the size of the hepatitis A virus (HAV)-susceptible working population and, thus, a constant decline in the expected annual number of hepatitis A cases. Implementation of a mass active vaccination policy would reduce the expected number of jaundice cases for the next 20 years by 6.9-fold, in comparison to the present policy of administration of immune globulin after an outbreak.
Measure of benefits used in the economic analysis Monetary benefits were assessed using the human capital approach.
Direct costs Direct costs were assessed for medical treatment of three types of cases: mild to moderate, severe, and fatal hepatitis A. These costs come from a study of 22 GPs in which costing was derived from a major sickness fund relating to employment costs and costs of laboratory tests. Costs of the vaccination programme were derived from separate sources. Discounting was carried out using a 5% rate and was relevant as the time horizon used in the model was 20 years. Estimation of quantities and costs was derived using modelling.
Statistical analysis of costs No statistical analysis was reported.
Indirect Costs Productivity losses were assessed using the human capital approach. Discounting was carried out using a 5% rate, and was relevant as the time horizon used in the model was 20 years. Costs and quantities were analysed separately and estimates were derived using modelling. Productivity loss was adjusted for expected unemployment by multiplying the duration of absence from work by the average employment rate.
Currency Original costs were in Israeli shekels but were converted to US dollars ($) at the April 2000 exchange rate of 4 shekels to 1 US dollar.
Sensitivity analysis Simulations of the model were apparently conducted and a break-even point for net present value (NPV) was presented. However, no further details were presented regarding sensitivity analyses and no further results were presented. The authors' justification for the lack of additional sensitivity analyses was the multitude of uncertain parameters in this study.
Estimated benefits used in the economic analysis As a cost-benefit analysis was performed the reader is referred to the synthesis of costs and benefits reported below.
Cost results The expected discounted cost of future hepatitis A cases, if the status quo prevention policy continued, was $2.145m, with a total net discounted cost of post-outbreak passive immunisation for the next 20 years of $70,408.
The expected cost of a mass vaccination campaign was $3,610,689, of which $3,070,689 was for vaccine and $540,000 for administration.
The total cost of the selective vaccination campaign was $1,145,866, of which $540,000 was for administration, $341,264 for serological tests, and $260,762 for vaccine.
Synthesis of costs and benefits The incremental cost of the selective vaccination strategy in comparison to passive immunisation was $1,075,458, resulting in a saving of $1,609,277 by reducing the future direct and indirect cost of hepatitis A. In a similar way, the additional $2,464,823 needed for the mass active vaccination strategy was expected to reduce only slightly the cost of future hepatitis A ($101,428) with a NPV of -$2,363,395 and a benefit-to-cost ratio of 0.04.
Authors' conclusions Under these study assumptions, the practice of administering hepatitis A active vaccine to serologically proven non-immune daycare centre workers has a cost-benefit justification, and should be widely considered in countries with a similar hepatitis A epidemiology to that in this study.
CRD COMMENTARY - Selection of comparators The choice of comparators was clearly stated with three alternatives being considered. The two alternatives commonly compared for vaccination strategies e.g. selective and mass vaccination programmes, were compared with the policy currently recommended by the Israeli Health Ministry for preventing hepatitis A spread in daycare centres. In addition, a selective vaccination strategy was expected to minimise the number of unnecessary active vaccines administered, while a mass strategy would eliminate the possibility that workers with a false-positive HAV-antibody test result would not be vaccinated.
Validity of estimate of measure of effectiveness It is difficult to assess the likely validity of this modelling study as the authors provided so little evidence about the methods used to retrieve studies. The two major studies used for effectiveness data were previous studies by the authors of this paper (there is little doubt, however, that these studies are both entirely relevant to the study question presented in this modelling analysis). There does not appear to be any justification as to how or why other sources of data were included or excluded from the review of material to include in the Markov model. Finally, the authors appear to have used data from the available studies selectively rather than describing how the effectiveness data from the primary studies were combined.
Validity of estimate of measure of benefit The authors provided their results within a cost-benefit analysis, but also presented the likely health benefits in terms of the reduction of jaundice cases due to the intervention. These were appropriately determined using the model.
Validity of estimate of costs All relevant categories of cost appear to have been included in the analysis. However, the generalisability of results is likely to be limited due to the lack of both sensitivity and statistical analyses of costs and quantities (the authors themselves stated that additional sensitivity analyses were not carried out due to the multitude of uncertain parameters in the model).
Other issues The authors compared their findings with one other study that found the estimated seroprevalence justifying a serological test was very similar to the result found in this study. Externalities were not included in the model even though the authors admitted that their inclusion might change the final conclusions in favour of a mass vaccination strategy.
Implications of the study The findings of the study suggest that the practice of administering hepatitis A active vaccine to serologically proven non-immune daycare centre workers has a cost-benefit justification and thus the authors recommend that this policy should be widely implemented in countries with a similar hepatitis A epidemiology. In addition, the problem of hepatitis A in daycare centres might be an example of how to perform cost-benefit analysis of vaccination programmes by using epidemiological models.
Source of funding Financial support from the Fulbright US-Israel Mutual Educational Fund.
Bibliographic details Chodick G, Lerman Y, Peled T, Aloni H, Ashkenazi S. Cost-benefit analysis of active vaccination campaigns against hepatitis A among daycare centre personnel in Israel. PharmacoEconomics 2001; 19(3): 281-291 Other publications of related interest Lerman Y, Chodick G, Aloni H, et al. Occupations at increased risk of hepatitis A: a 2-year nationwide historical prospective study. American Journal of Epidemiology 1999;150(3):312-20.
Peled T, Lerman Y, Chodick G, et al. Sero prevalence of hepatitis A antibodies among day-care center workers. EPICOH, 14th International Conference on Epidemiology in Occupational Health; 1999 Oct 10-14; Herzlia.
Indexing Status Subject indexing assigned by NLM MeSH Adolescent; Adult; Aged; Child Day Care Centers; Cost-Benefit Analysis; Female; Hepatitis A /prevention & Hepatitis A Vaccines /immunology; Humans; Middle Aged; Vaccination; control AccessionNumber 22001008108 Date bibliographic record published 30/11/2001 Date abstract record published 30/11/2001 |
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