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Cost-benefit analysis of a Haemophilus influenzae type B meningitis prevention programme in the Philippines |
Limcangco M R M T, Armour C L, Salole E G, Taylor S 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 Two strategies against Haemophilus Influenzae Type B (Hib) Meningitis were compared: a government-funded vaccination programme, and a no vaccination programme.
Study population The study population was a birth cohort of 100,000 children in Manila, Philippines. The state of health of the cohort with and without a Hib immunisation programme was modelled over a 5-year period. The authors stated that a 5-year cohort was used because meningitis infection most often occurs in this age range. The authors did not report any inclusion or exclusion criteria.
Setting The study was set in primary care in Manila, The Philippines.
Dates to which data relate Efficacy and resource use data were taken from literature published between 1989 and 2000. The price year used was 1998.
Source of effectiveness data The study was based on a review/synthesis of completed studies.
Modelling A model was used in order to estimate the number of cases that would occur with and without the immunisation programme. The authors presented a simplified diagram of their model in the form of a tree diagram. Each month the children in the cohort have a given risk of developing Hib meningitis. If the child develops the infection he or she has a given probability of developing either, severe or mild sequelae, of dying, or of a full recovery. Those who develop Hib meningitis leave the cohort of children at risk of infection for the succeeding months. Those who do not develop the infection form the population at risk in the succeeding month. The cycle continues until the children in the cohort reach the sixtieth month.
Outcomes assessed in the review The following outcomes were assessed in the review:
Hib meningitis incidence per 100,000 children under 5 years old;
probability of all causes of childhood mortality per 100,000 birth cohort for children under 1 year of age, and children 1-5 years of age;
case fatality rate;
probability of no sequelae;
probability of sequelae;
probability of severe sequelae;
probability of moderate sequelae;
life expectancy;
life expectancy with full recovery;
life expectancy with moderate sequelae;
life expectancy with severe sequelae;
vaccine effectiveness; and
vaccine coverage.
Study designs and other criteria for inclusion in the review The authors did not report the study designs to be included in the review or any inclusion or exclusion criteria for the review carried out to estimate the probability values for the model. The authors stated that a survey of medical records of patients with Hib meningitis in Manila was also used to provide data on the extent of sequelae following infection.
Sources searched to identify primary studies The authors did not report the sources searched or the search strategy used to identify studies for the synthesis of data.
Criteria used to ensure the validity of primary studies The authors did not report the criteria used to judge the validity of studies included in the synthesis of data.
Methods used to judge relevance and validity, and for extracting data The authors did not report the criteria used to judge the relevance of data or determine which data were extracted.
Number of primary studies included The authors referenced 6 published studies for the outcomes estimated in the review.
Methods of combining primary studies The method of combining data from more than one source was not described.
Investigation of differences between primary studies The authors stated that hearing loss, originally categorised as a severe sequelae in the epidemiological study used in the review, was reclassified as a less severe outcome in order to conform to the classification used by the other studies. The authors did not report any other information about investigation of differences between primary studies.
Results of the review The study reported the following results of the review:
Hib meningitis incidence per 100,000 children under 5 years old: 95;
probability of all causes of childhood mortality per 100,000 birth cohort: children under year of age: 0.0582, and children 1-5 years of age: 0.0168;
case fatality rate: 0.110;
probability of no sequelae: 0.828;
probability of sequelae: 0.172;
probability of severe sequelae: 0.388;
probability of moderate sequelae: 0.612;
life expectancy: 65 years;
life expectancy with full recovery: 65 years;
life expectancy with moderate sequelae: 50 years;
life expectancy with severe sequelae: 40 years;
vaccine effectiveness: 90%; and
vaccine coverage: 85%.
Measure of benefits used in the economic analysis The authors reported the reduction in the number of new cases of Hib meningitis per year if a vaccine programme was introduced. The authors valued severe sequelae and mortality from Hib meningitis in monetary terms using a human capital approach. These are indirect costs and details are given below.
Direct costs The authors did not report all resource use and costs separately. Some details of resource use were reported in the text. The authors included the following costs to the government in the model: initial visit to general practitioner, vaccine administration, hospitalisation, and special education for children with moderate sequelae. The authors also included the following direct costs to society in the model: transportation, loss of income of parents while their child is in hospital, hearing aid, doctors follow-up and drugs, residential care for children with severe sequelae, and loss of income of a parent to provide care for children with severe sequelae.
Hospital costs were determined from the Philippine General Hospital costs. The marginal cost of special education and of long term care in Manila was conservatively estimated. The costs of parent's time of work were estimated from annual earnings, based on the minimum wage.
The price year used was 1998. All future costs were discounted at a rate of 5% per year.
Statistical analysis of costs No statistical analysis of costs was reported.
Indirect Costs Annual earnings based on the minimum wage were estimated from the age of 20 to 65 and were applied to those children who died or had severe sequelae. This was adjusted to reflect the national unemployment rate of 9%. The authors did not state how the adjustment was made.
All future costs were discounted at a rate of 5% per year.
Currency Philippine pesos (PHP). A conversion rate of US$1 = PHP35 (1998 exchange rate) was reported.
Sensitivity analysis The authors conducted a one way sensitivity analysis to test the impact of variability in the data on the results. The analysis was conducted by changing the values of the following parameters: efficacy, Hib meningitis incidence rate per 100,000 children under 5 years of age, vaccination rate, discount rate and vaccine price. The 95% confidence interval was used to determine the upper and lower sensitivity values for Hib meningitis incidence rates and vaccine efficacy.
Estimated benefits used in the economic analysis The study reported that, in the absence of a preventative intervention against Hib meningitis, there would be 980 new cases per year for a 100,000 birth cohort in Manila. This would be reduced to 427 cases per year for the next 5 years if a 3-dose Hib vaccination programme that aims to vaccinate at 2, 3 and 4 months were introduced.
Cost results The total Hib costs for the 100,000 birth cohort was PHP1,071,541,377 without Hib immunisation and PHP527,165,711 with immunisation, discounted at 5% per year. The incremental costs of vaccination were -PHP39 million from the government perspective and -PHP255.4 million from the societal perspective (direct costs only).
Synthesis of costs and benefits The study reported that the results of the cost-benefit analysis showed that the cost of implementing Hib conjugate vaccination is less than the cost of Hib meningitis to both the government and to society. The net savings from a societal perspective, including direct and indirect costs were PHP560.0 million.
Authors' conclusions The study reported that there would be a positive economic benefit for the Philippine government and for the Filipino society if a Hib vaccination programme were introduced in Manila. The authors, therefore, stated that, in the absence of other government projects with a higher benefit to cost result, the Philippine government should consider including Hib conjugate vaccine in its immunisation programme.
CRD COMMENTARY - Selection of comparators A justification was given for the comparator used, namely that the vaccination could prevent Hib meningitis and therefore reduce the high incidence rate of the infection in children under 5 years old in the Philippines, where there was no vaccination programme. You as a user of this database, should decide if a no vaccination programme is a relevant comparator 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, only that data from an epidemiological study conducted in Manila were used. It was therefore unclear if the review was conducted in a systematic way to identify relevant research and minimise bias. The authors did not state whether the estimates of outcomes from different studies were combined or whether they used data from the available studies selectively. The authors did report that there were differences between studies for the classification of hearing loss. They did not explicitly report differences between primary studies in other variables. The authors noted that a number of factors were not included in the review or model of effectiveness. These were partial protection from 1 or 2 doses of the vaccine, the impact of herd immunity or the impact of the vaccine on other Hib infections such as pneumonia. The authors also noted that excluding these factors was conservative and biased the analysis against the vaccine programme.
Validity of estimate of measure of benefit The authors used monetary valuation of mortality and severe sequelae as the measure of health benefit and noted that this was based on lost productivity for these events only and did not include the value of distress, pain and grief to children or parents, or external benefits to other members of society.
Validity of estimate of costs The authors did not clearly present resource use and price data separately. All categories of cost relevant to the perspective adopted were included in the analysis and the authors discounted future costs. The cost estimates were derived from published sources, health care data and assumption. The authors did not clearly report the methods used to estimate direct and indirect costs. The values used for hospital costs and indirect costs and discount rate were tested in the sensitivity analysis. The authors reported that the price year used was 1998, but did not report whether any of the costs items included in the analysis were derived from data from different price years.
Other issues The authors stated that the study was similar to a number of economic studies on Hib vaccination, in that it developed a model to stimulate the effects of a vaccination programme in a birth cohort. The authors used a similar model to that used in other studies, which was validated for the Philippines by expert opinion. The authors noted that there were differences in the epidemiological variables used. Differences included the fact that this study concentrated on Hib meningitis alone and that the incidence rates in this study were at least two-fold higher than those used in previous economic studies.
The authors stated explicitly that, due to the fact that the epidemiology and costs associated with Hib meningitis vary between countries, the generalisability of the results of this study is limited.
The authors appear to have presented their results selectively.
The study considered children under 5 years of age in the Philippines and this was reflected in the authors' conclusions.
Implications of the study The authors stated that, in developing countries, any intervention should be thoroughly evaluated so as not to waste limited resources. This study has shown that there would be positive economic benefit in Manila and the Philippine society if a Hib vaccination programme were introduced. The results therefore have important implications for the decision-making process.
Bibliographic details Limcangco M R M T, Armour C L, Salole E G, Taylor S J. Cost-benefit analysis of a Haemophilus influenzae type B meningitis prevention programme in the Philippines. PharmacoEconomics 2001; 19(4): 491-400 Indexing Status Subject indexing assigned by NLM MeSH Algorithms; Child, Preschool; Cost-Benefit Analysis; Haemophilus Vaccines; Humans; Immunization Schedule; Incidence; Infant; Meningitis, Haemophilus /economics /prevention & Philippines /epidemiology; control /epidemiology AccessionNumber 22001008088 Date bibliographic record published 28/02/2002 Date abstract record published 28/02/2002 |
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