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Influenza vaccination programs for elderly persons: cost-effectiveness in a health maintenance organization |
Mullooly J P, Bennett M D, Hornbrook M C, Barker W H, Williams W W, Patriarca P A, Rhodes P H |
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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 Vaccination against influenza.
Economic study type Cost-effectiveness analysis.
Study population Elderly males and females (aged 65+). High risk participants werethose who had medical care contacts for chronic pulmonary, cardiovascular, metabolic, renal or malignant conditions.
Setting Hospital and the community. The study was conducted in the Portland, Oregon, Vancouver and Washington areas, USA and Canada.
Dates to which data relate 9 periods (8 epidemic and 1 non-epidemic) between October 1980 and March 1989. The price year was 1985.
Source of effectiveness data Link between effectiveness and cost data Costs were calculated retrospectively on the same population as the effectiveness study.
Study sample The population was stratified for risk and consisted of between 21,009 and 37,587 participants over the study period (a total of 251,034 person-periods). Cases were inpatients with influenza and pneumonia during the study period and outpatients (from 5% random sample of all HMO elderly plan members) attending with influenza and pneumonia. Controls were members of the 5% sample who were neither hospitalized or attending outpatients for influenza and pneumonia. Power calculations were not used in determining sample size.
Analysis of effectiveness The analysis of the clinical study was based on intention to treat. Outcomes were influenza and pneumonia episodes prevented (judged by admissions, deaths and outpatient contacts). Effectiveness was expressed as the difference in relative risk for pneumonia and influenza episodes in vaccinated and unvaccinated populations. Logistic analysis controlled for high risk status, influenza and pneumococcal vaccine status, age, sex and length of observation time.
Effectiveness results Overall, among high risk elderly, influenza vaccination was 30% (CI:17% to 42%) effective in preventing hospitalization and 33% (CI: -7% to 58%) effective in preventing death due to pneumonia and influenza. Among non-high-risk elderly the effectiveness in preventing hospitalization due to pneumonia and influenza was 40% (CI: 1% to 64%). However during high epidemic seasons the effectiveness ranged from 83% (CI: 54% to 94%) to 51% (CI: 13% to 73%) in preventing hospitalizations among high risk elderly.
Clinical conclusions The effectiveness of the vaccine appears to be higher at the height of epidemics in non high-risk elderly patients
Measure of benefits used in the economic analysis Prevented outpatient episodes, in-hospital deaths and hospital admissions.
Direct costs For all inpatients, costs were derived from the Kaiser Permanente (HMO) accounting system. For outpatients costs were derived from 5% random sample. Quantities and unit costs (derived from the accounting system) were defined separately but were not shown as such. No discounting was undertaken. Vaccination campaign costs included overheads and publicity costs.
Estimated benefits used in the economic analysis The estimated benefits were: outpatient episodes prevented: 194, 135 and 329 for high risk, non-high risk and all elderly respectively;
Hospitalizations prevented: 83, 12, 95 for high risk, non-high risk and all elderly respectively
Inhospital deaths prevented: 31, 2 and 15 for high risk, non-high risk and all elderly respectively
Cost results Overall the total medical care cost for pneumonia and influenza per person-period was $45.50 and $5.14 for high-risk and non high-risk patients respectively. For all elderly the total cost was $21.27. Overall the programme generated a net saving of $ 6.11 (CI: -$0.23 to $11.53) per vaccination of high-risk persons achieved and $1.10 for all elderly persons. For non high-risk the cost exceeds the saving by $4.82 (CI: $3.34 to $7.06). Such conclusions are sensitive to the vaccine effectiveness estimates. The total costs for high-risk, non high-risk and all elderly respectively were as follows:
total cost of vaccine programme - $37,517, $31,748 $69,264;
cost per vaccination - $7.11, $7.11, $7.11;
cost of vaccination programme per member per month - $0.19, $.13, $0.15.
Synthesis of costs and benefits Cost effectiveness results overall (all years) for high-risk, non high-risk and all elderly were as follows:
cost per outpatient episode prevented - $1,375, $1,673, $1,497;
cost per in-hospital death prevented - $21,347, $150,539, $35,189;
cost per hospitalization prevented - $3,234, $18,817, $5,213.
Authors' conclusions The vaccine programme for high-risk elderly is cost-saving and the small net cost of the non-high-risk elderly is likely to be recouped by indirect benefits (e.g. prevention of suffering, incapacity and loss of wages). The authors believe that the study proves that there is financial incentive to vaccinate all elderly HMO members against influenza.
CRD Commentary The validity of this study is very difficult to assess. It is, for instance, unclear on what basis cases and controls were matched and whether retrospectively gathered data were sufficient to answer the study questions. We have no visibility of resource estimates as the basis of the costs and cost structures reflect those of the HMO with charge elements in them. For these reasons, as acknowledged by the authors, caution should be exercised when generalising from this study. Additionally, costs mentioned are likely to be average and not marginal, leading to a likely overestimation of the benefits of the programme. The choice of case-control design is explained by the fact that as the FDA recommends influenza vaccine for the elderly, RCTs or CCTs are considered unethical in the USA.
Source of funding Supported in part by the Centers for Disease Control Contract 200-89-0748.
Bibliographic details Mullooly J P, Bennett M D, Hornbrook M C, Barker W H, Williams W W, Patriarca P A, Rhodes P H. Influenza vaccination programs for elderly persons: cost-effectiveness in a health maintenance organization. Annals of Internal Medicine 1994; 121(12): 947-952 Indexing Status Subject indexing assigned by NLM MeSH Aged; Case-Control Studies; Cost-Benefit Analysis; Female; Health Care Costs; Health Maintenance Organizations /economics; Humans; Influenza Vaccines /economics; Influenza, Human /prevention & Male; Northwestern United States; Pneumonia, Viral /prevention & Regression Analysis; Risk Factors; Vaccination /economics; control; control AccessionNumber 21995000041 Date bibliographic record published 30/09/1998 Date abstract record published 30/09/1998 |
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