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Age, revaccination, and tolerance effects on pneumococcal vaccination strategies in the elderly: a cost-effectiveness analysis |
Smith KJ, Zimmerman RK, Nowalk MP, Roberts MS |
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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. CRD summary The objective was to assess the cost-effectiveness of single- and multiple-dose pneumococcal polysaccharide vaccination strategies, for those aged over 65 years. The authors concluded that for patients aged 65 to 80 years, a single-dose vaccination was clinically and economically reasonable. The methods were appropriate, but there were a large number of sources and interventions, and only brief details of the methods and results were provided. Given the scope of the analysis, it seems that the authors’ conclusions are valid. Type of economic evaluation Study objective The objective was to assess the cost-effectiveness of single- or multiple-dose pneumococcal polysaccharide vaccination strategies in three cohorts of patients, one aged 65 years, one aged 75 years, and one aged 80 years, for the prevention of invasive pneumococcal disease. Interventions Ten vaccination strategies were investigated for 65-year-olds: no vaccination; one vaccination; two vaccinations at ages 65 and 70 years, 65 and 75 years, 65 and 80 years, or 65 and 85 years; three vaccinations at ages 65, 70 and 75 years, 65, 71 and 77 years, or 65, 75 and 85 years; and four vaccinations at ages 65, 70, 75 and 80 years.
Four strategies were investigated for 75-year-olds: no vaccination; one vaccination; and two vaccinations at ages 75 and 80 years, or 75 and 85 years.
Three strategies were investigated for 80-year-olds: no vaccination; one vaccination; and two vaccinations at ages 80 and 85 years. Methods Analytical approach:A decision-analytic Markov model was used to estimate the cost-effectiveness each of the pneumococcal vaccination strategies for the three age cohorts. The time horizon was the lifetime of the patient. The authors reported that a societal perspective was adopted.
Effectiveness data:The effectiveness data were derived from a number of sources. Age-related comorbidity and mortality, for the oldest groups, were based on data from the Framingham study and the Surveillance, Epidemiology and End Results (SEER) database. Age- and comorbidity-specific invasive pneumococcal disease incidence and mortality data were from the Active Bacterial Core surveillance (ABCs) programme of the Centers for Disease Control and Prevention (CDC). The invasive pneumococcal disease-related disability and disease rates, with no vaccination, and the vaccine serotype coverage were also based on data from the CDC. Estimations for the adverse events with the vaccine were from published studies. Further details of the data sources were reported in Smith, et al. (2008, see 'Other Publications of Related Interest' below for bibliographic details). The main effectiveness estimate was the vaccination effectiveness, which was assumed by an expert panel.
Monetary benefit and utility valuations:The quality-of-life weights, used to value the utilities, were from published studies.
Measure of benefit:The primary measure of benefit was the quality-adjusted life-year (QALY) and these were discounted at a rate of 3% per annum.
Cost data:The costs were those that related to: vaccination and administration; treatment of invasive pneumococcal disease for those who were discharged from hospital; and treatment for those who died in hospital. The authors did not list the costs included in these categories. The costs were from published studies and the Healthcare Cost and Utilization Project (HCUP). The price year was 2003 and all costs were reported in US dollars ($) and were discounted at an annual rate of 3%.
Analysis of uncertainty:A series of one-way sensitivity analyses were performed by varying all the model parameters individually. A probabilistic sensitivity analysis was undertaken by applying distributions to the model parameters and sampling these simultaneously 3,000 times. Expert panel estimates for vaccine effectiveness were varied using triangular distributions and the parameters that were from clinical trial or epidemiological data were varied using distributions based on their characteristics. The results of the probabilistic sensitivity analysis were presented in a cost-effectiveness acceptability curve. A separate sensitivity analysis, which relaxed some of the base-case assumptions, was also undertaken and summarised in a bar chart. Results All dominated strategies, which were more costly and less effective than another strategy, were excluded. Compared with no vaccination, vaccination of 65-year-olds once had an incremental cost-utility ratio (ICUR or cost per QALY gained) of $26,100. Vaccination of 75-year-olds once had an ICUR of $71,300 and vaccination of 80-year-olds once had an ICUR of $75,800.
For 65-year-olds, the ICUR was $88,400 for vaccination at ages 65 and 75 years, compared with the single vaccination. It was $115,000 for vaccination at ages 65, 75, and 85 years, compared with the two vaccinations, and $215,000 for vaccination at ages 65, 70, 75, and 85 years, compared with the three vaccinations. For 75-year-olds, the ICUR was $92,700 for vaccination at ages 75 and 85 years, compared with the single vaccination. For 80-year-olds, the ICUR was $548,000 for vaccination at ages 80 and 85 years, compared with the single vaccination.
The probabilistic sensitivity analysis showed that vaccination at 65 years was cost-effective over a range of acceptability thresholds between $30,000 and $90,000 per QALY gained. Vaccination at 65 and 75 years was cost-effective over a range of acceptability thresholds between $100,000 and $160,000 per QALY gained. Vaccination at 65, 70, 75, and 80 years was cost-effective above a threshold of $170,000 per QALY gained.
In the separate sensitivity analysis, which assumed prior vaccination and a 20% loss of vaccine effectiveness, vaccination of the 65-year-old cohort, three times at 65, 75, and 85 years, became unacceptable at the willingness-to-pay threshold of $150,000 per QALY gained. All vaccination strategies, except for the single vaccination of 65-year-olds, became unacceptable at a willingness-to-pay threshold of $100,000 per QALY gained. Authors' conclusions The authors concluded that for patients aged 65 to 80 years a single-dose vaccination was clinically and economically reasonable. CRD commentary Interventions:The interventions were reported clearly and the usual practice was included.
Effectiveness/benefits:The effectiveness data were from a number of sources and no search strategy was reported, making it difficult to determine if all the relevant information was included. The authors provided little information about the data, but referenced another publication for more details and, without reviewing this publication, it is not possible to determine the quality of these data. The method used to elicit the preferences for the QALYs was not reported, which makes it difficult to determine if they accurately measured the health outcome.
Costs:A societal perspective was adopted, but the authors did not report the cost items included, which means that it was unclear whether all those costs relevant to this perspective were included. The sources, from which the costs were obtained, were reported. The price year, time horizon, and discount rate were all reported.
Analysis and results:The available costs and outcomes were synthesised using a Markov model. Adequate details of the model structure were reported, including a diagram. The costs and outcomes of the model were not reported separately. The impact of uncertainty on the model’s results was adequately tested, using one-way sensitivity analyses and a probabilistic sensitivity analysis. The authors reported the limitations of their study, the main one being that the effectiveness of vaccination was assumed by an expert panel.
Concluding remarks:The methods were appropriate. There were a large number of sources and interventions, and the authors only provided brief details of their methods and summarised their results. Given the scope of the analysis, it appears that the authors’ conclusions are valid. Bibliographic details Smith KJ, Zimmerman RK, Nowalk MP, Roberts MS. Age, revaccination, and tolerance effects on pneumococcal vaccination strategies in the elderly: a cost-effectiveness analysis. Vaccine 2009; 27(24): 3159-3164 Other publications of related interest Smith KJ, Zimmerman RK, Lin CJ, Nowalk MP, Ko FS, McEllistrem MC, et al. Alternative strategies for adult pneumococcal polysaccharide vaccination: a cost-effectiveness analysis. Vaccine 2008; 26(11): 1420-1431. Indexing Status Subject indexing assigned by NLM MeSH Age Factors; Aged; Aged, 80 and over; Cost-Benefit Analysis; Humans; Immune Tolerance; Pneumococcal Vaccines /economics /immunology; Probability; Quality-Adjusted Life Years; Vaccination /economics AccessionNumber 22009101773 Date bibliographic record published 05/08/2009 Date abstract record published 10/11/2010 |
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