Source of effectiveness data The effectiveness data were derived from a review or synthesis of completed studies.

Transcription

1 The 23-valent pneumococcal polysaccharide vaccine. Part II: a cost-effectiveness analysis for invasive disease in the elderly in England and Wales Melegaro A, Edmunds W J 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 vaccination of all people over the age of 65 years with the 23-valent pneumococcal polysaccharide vaccine (PPV) was examined. Type of intervention Primary prevention. Economic study type Cost-effectiveness analysis. Study population The study population comprised all persons aged over 65 years. Setting The setting was primary care. The study assessed the clinical and economic implications of the intervention in England and Wales. Dates to which data relate The effectiveness of the intervention was derived from primary data collected between 1991 and 1998 and papers published between 1980 and The resource use data related to 1995 to The prices related to Source of effectiveness data The effectiveness data were derived from a review or synthesis of completed studies. Modelling A model was used to establish the clinical and cost implications of the intervention. It followed two hypothetical cohorts (i.e. vaccinated and unvaccinated) of people aged 65 years and over, until their death. The hypothetical cohorts were each divided into two distinct sub-groups, a high-risk group (HRG) and a non high-risk group (NHRG) Outcomes assessed in the review The model parameters identified were: vaccine efficacy; the duration of protection offered by the vaccine; Page: 1 / 6

2 the prevalence and life expectancy of high- and low-risk groups; the proportion of population at high risk and low risk of pneumococcal infections; the incidence of pneumococcal infections; and mortality from pneumococcal infections. Study designs and other criteria for inclusion in the review The incidence of invasive pneumococcal infections was taken from the HPA communicable Disease Surveillance Centre's Respiratory and Systemic Infection Laboratory. The prevalence and life expectancy of high- and low-risk groups were taken from the Morbidity Statistics from General Practices, a 1-year survey of general practices (GPs) in England and Wales covering over 500,000 individuals. Vaccine efficacy and duration of protection were assessed by reviewing randomised and quasi-randomised trials and case-control studies. As the majority of these studies were insufficiently powered to detect any effect of PPV against invasive pneumococcal diseases, a pooled estimate was obtained using a random-effects model (see Other Publications of Related Interest). Sources searched to identify primary studies The authors did not search specific databases to identify primary studies. Criteria used to ensure the validity of primary studies Not reported. Methods used to judge relevance and validity, and for extracting data Not reported. Number of primary studies included The parameters used in the model were derived from two primary data sources and seven published papers. Methods of combining primary studies Data from the primary sources was either taken from a single source or obtained using a random-effects model. Investigation of differences between primary studies The authors verified the overall mortality rate of their population derived from one data source with data from the 1991 census. The methods used were not reported in the paper. Results of the review Vaccine efficacy was 20% in the HRG and 65% in the NHRG. The duration of protection offered by the vaccine was 5 years in the HRG and 6.5 years in the NHRG. The high estimates of mortality ranged from 16 to 28% in the HRG, and from 15 to 24% in the NHRG. The low estimates of mortality ranged from 8 to 20% in the HRG, and from 9 to 20% in the NHRG. The prevalence of HRG was 9.6% for age group years, 9.7% for age group years, 10.2% for age group years, 9.7% for age group years, and 7.7% for age group above 85 years. Page: 2 / 6

3 Measure of benefits used in the economic analysis The measure of health benefit used was the number of life-years gained (LYG). The health benefits were discounted at a rate of 3% per annum. Direct costs This study assessed the costs of the vaccine and pneumococcal infections to the health care provider. The costs and the quantities were reported separately. The cost of the vaccine was taken from the British National Formulary. It was assumed that the vaccine would be given at the same time as the influenza vaccine and, therefore, there would not be any additional costs to primary care. The costs of infection included GP visits, GP prescriptions and hospital admission costs associated with pneumococcal infections. It was assumed that all cases of pneumococcal infection would result in one visit to a GP and one prescription for antibiotics prior to hospital admission. The unit cost of a GP visit was taken from the Unit Costs of Health and Social Care. The unit cost of antibiotics was taken from the British National Formulary. The proportion of people who would be admitted to hospital was derived from Hospital Episode Statistics for April 1995 to March 1998, as was the length of stay on general and intensive care wards. The unit of cost per day in each type of ward was taken from the Unit Costs of Health and Social Care. Adverse effects of the vaccine were noted to be minimal and were therefore excluded from this analysis. Owing to a lack of data, the costs associated with longterm care for sequelae of invasive pneumococcal diseases were not included. The price year was 2000 for all items. The costs were discounted at a rate of 3% per annum. Statistical analysis of costs The cost data were treated deterministically. Indirect Costs No indirect costs were included in this study. Currency UK pounds sterling (). Sensitivity analysis Both one- and multi-way sensitivity analyses were undertaken to assess variability in the data and the generalisability of findings. The parameters used in the sensitivity analysis represented minimum and maximum values taken from the primary data sources. The variables in this analysis were: vaccine efficacy; the duration of vaccine protection; the definition of patients with infection; the hospital admission rate; the mortality rate; the length of hospitalisation; the proportion of patients admitted to intensive care; the cost of the vaccine and delivery; the cost of inpatient stay; Page: 3 / 6

4 the cost of GP consultation and antibiotic prescription; and the discount rate. The authors also looked at the incremental costs and benefits of introducing regular booster doses at specific intervals (5 and 10 years) and assessed the optimum interval for revaccination. Estimated benefits used in the economic analysis The authors did not report the estimated number of LYG in a non synthesised manner. Cost results The net discounted cost of vaccinating all people aged 65 years or older was 2,485,655. This comprised 3,163,165 for vaccinating the cohort, offset by discounted medical care savings of 677,510 over the lifetime. The net discounted cost of only vaccinating high-risk people aged 65 or older was 215,002. This was made up of 302,291 for the vaccination, offset by 87,289 in discounted medical care savings. Synthesis of costs and benefits The clinical and economic evidence in this study were synthesised to give the cost per LYG of the two options. Each LYG would cost 8,504 if all elderly people were vaccinated with PPV, compared with 9,477 for each LYG when only high-risk elderly patients were vaccinated. Only two parameters altered in the sensitivity analysis affected the conclusion that vaccination of all people aged 65 or older was dominant. The intervention was no longer dominant if the proportion of patients admitted to intensive care was raised to 40%, and if the discount rate for the benefits and costs was increased to 6%. The authors also reported that the results were very much dependent on the uncertainty around vaccine efficacy estimates, especially in the HRG. Incremental cost-effectiveness ratios of between 17,000 and 26,000 were estimated for both groups of elderly when revaccinating every 10 years. Higher incremental cost-effectiveness ratios (23,000-61,000) were produced when considering a revaccination policy every 5 years. Authors' conclusions The vaccination of all people over the age of 65 years with the pneumococcal polysaccharide vaccine (PPV) is a costeffective intervention. CRD COMMENTARY - Selection of comparators The authors compared the intervention with current practice in the study setting. You should consider how this relates to current practice in your own setting. Validity of estimate of measure of effectiveness The authors derived clinical effectiveness data from a model. Primary data sources and published studies were used to obtain the input parameters. However, the published papers were not selected from a systematic review of the literature. One of the papers was a random-effects model combining randomised and quasi-randomised trials, which was undertaken by the same authors. The authors did not provide details of any criteria that they used to choose primary studies to obtain the input parameters for their model. They appear to have undertaken their own analysis on the primary data sources, although the details reported were limited. Validity of estimate of measure of benefit The LYG were used as the measure of benefit in the economic analysis. The decision analytic model used to derive Page: 4 / 6

5 these estimates appears to have been appropriate. Validity of estimate of costs The study was conducted from the perspective of the health care provider. All the categories of cost relevant to the perspective adopted were included in the analysis, and all the relevant costs appear to have been included. However, owing to a lack of data, the costs associated with long-term care for sequelae of invasive pneumococcal diseases were not included. In addition, the impact of adverse reactions to vaccination was not considered in the study, as such reactions were judged to be minimal. The exclusion of the costs of complications might have led to an underestimation of the cost-effectiveness of vaccination of HRGs. The costs and the quantities were reported separately, which will enhance the generalisability of the authors' results. A clear price year was reported, which will facilitate future reflation exercises. A thorough sensitivity analysis assessed the variability of maximum and minimum values from the model, and was therefore appropriate. This increases the generalisability of the study findings. Both the future costs and benefits were discounted as recommended by the US Panel on Cost-effectiveness. Other issues The authors did not compare their findings with other published studies, nor did they consider how their results could be generalised. However, the study was designed to assess the impact of the intervention across England and Wales. The authors do not appear to have presented their results selectively and their conclusions reflected the scope of the analysis. The authors did not report any further limitations to their study. Implications of the study The authors suggested that the vaccination of all people over the age of 65 years should replace the policy of limiting vaccination to those at high risk of infection. In addition, giving a booster dose of the vaccine every 10 years could be an economically sensible policy to adopt. The authors also suggest that further work, to better estimate the causes of death in hospitalised patients, could be performed. Source of funding Supported by the MRC (grant G ) and the EU (grant QLG4-CT ). Bibliographic details Melegaro A, Edmunds W J. The 23-valent pneumococcal polysaccharide vaccine. Part II: a cost-effectiveness analysis for invasive disease in the elderly in England and Wales. European Journal of Epidemiology 2004; 19(4): PubMedID Other publications of related interest Melegaro A, Edmunds WJ. The 23-valent pneumococcal polysaccharide vaccine: Part 1. Efficacy of PPV in the elderly: a comparison of meta-analyses. European Journal of Epidemiology 2004;19: Indexing Status Subject indexing assigned by NLM MeSH Aged; Aged, 80 and over; Cost-Benefit Analysis; Decision Support Techniques; England; Humans; Pneumococcal Infections /economics /epidemiology /prevention & control; Pneumococcal Vaccines /economics; Public Health; Wales AccessionNumber Page: 5 / 6

6 Powered by TCPDF ( Date bibliographic record published 31/05/2005 Date abstract record published 31/05/2005 Page: 6 / 6