A pharmacoeconomic model for the treatment of influenza

Efficacy of influenza vaccine among elderly patients by physical activity status

OBJECTIVE

Although many studies have shown the usefulness of influenza vaccine in elderly in-patients, the efficacy of vaccination with regard to the daily physical activities of patients has not been fully evaluated. To address this issue, we correlated the use of medical resources with vaccination status in patients categorized according to their daily activity levels.

METHODS

The subjects comprised 237 in-patients at or above 51 years of age, who were hospitalized in the long-term care unit of a Japanese hospital between January and March, 1999. The vaccination status and medical resources use (i.e., oral antibiotics, injected antibiotics, blood cell count, chest X-ray) of each patient were recorded, and the patients were assigned to three subgroups, based on daily life activity scores.

RESULTS

Vaccinated in-patients in the 'bed-bound' category required fewer medical resources, i.e., oral antibiotics (-2.29 days,P<0.05), injected antibiotics (-5.02 days,P<0.001), blood cell counts (-4.66 times,P<0.001), and chest X-rays (-4.31 times,P<0.001), compared with unvaccinated in-patients. There were no significant differences in treatment parameters between vaccinated and unvaccinated patients in the 'partly limited' or 'no limitation' categories.

CONCLUSIONS

It is suggested that influenza vaccination significantly reduces the need for medical treatment only among those in-patients who are the least physically active. Further studies are required to replicate these findings, and to elucidate the underlying reasons for this reduction.

Clinical and socioeconomic impact of seasonal and pandemic influenza in adults and the elderly

Influenza epidemics and pandemics carry a heavy socioeconomic burden. Hospitalization and treatment are more often necessary in high-risk patients, such as the elderly. However, the impact of influenza is not negligible even in adults, mainly because of lost productivity. The World Health Organization estimates that seasonal influenza causes 250,000-500,000 deaths worldwide each year; however, mortality may be very high in pandemic periods. Many estimates of the costs of seasonal influenza have been made in various socioeconomic contexts. For instance, among the adult population in Italy, a cost of €940.39 per case has been estimated. In the US, the average annual influenza burden in 18-49-y-old adults without underlying medical conditions is judged to include approximately 32,000 hospitalizations and 680 deaths. Estimating the influenza burden is a useful aid to determining the best influenza vaccination strategy and preventive and clinical treatments.

Oseltamivir for influenza postexposure prophylaxis: economic evaluation for children aged 1-12 years in the U.S

BACKGROUND

Postexposure prophylaxis (PEP) with oseltamivir (Tamiflu) has been shown to be effective and is approved in children exposed to a case of influenza in a household setting. Given limited healthcare budgets, it is important to understand the costs and cost effectiveness of PEP in children.

PURPOSE

This study aims to estimate the cost effectiveness of oseltamivir PEP for children aged 1-12 years in the U.S.

METHODS

A decision-tree model with a 1-year time horizon was used to assess the cost effectiveness of oseltamivir PEP for 10 days at approved doses compared with no prophylaxis for children aged 1-12 years who were exposed to a household index case of influenza from the U.S. societal and payer perspectives. Model inputs included U.S. influenza epidemiology data, efficacy data from oseltamivir PEP clinical trials, direct medical resource use and costs for PEP and influenza treatment derived from large U.S. databases, and indirect costs based on caregiver lost productivity. Base-case estimates were tested in extensive sensitivity analyses.

RESULTS

For the societal perspective, the model estimated 12,184 fewer cases of influenza per 100,000 children exposed and an incremental cost-effectiveness ratio of $41,452 per quality-adjusted life-year (QALY) gained. Results were most sensitive to the influenza attack rate, PEP protective efficacy, and prescribing patterns for initiating PEP. Probabilistic sensitivity analyses showed that oseltamivir PEP was likely to be cost effective for all willingness-to-pay threshold values above $34,300 per QALY gained. Results were similar for the payer perspective.

CONCLUSIONS

Although there is no official cost-effectiveness threshold in the U.S., results from the current study show that when compared with no prophylaxis, oseltamivir PEP for children has cost-effectiveness ratios similar to those of vaccines for preventing influenza.

Cost-effectiveness of treating influenzalike illness with oseltamivir in the United States

PURPOSE

The cost-effectiveness of treating influenzalike illness (ILI) with oseltamivir in the United States was assessed.

METHODS

A decision-analysis model was developed with a one-year time horizon to assess the cost-effectiveness of oseltamivir compared with usual care from societal and payer perspectives for four patient populations: high-risk adults, healthy adults, elderly adults, and children. The model used efficacy data from oseltamivir clinical trials and other published literature and assumed oseltamivir was effective only in individuals infected with influenza virus not resistant to oseltamivir and treated within 48 hours of symptom onset. Direct medical costs were based on resources used; indirect costs were estimated based on time lost from work due to illness and premature mortality. Base-case estimates were tested in one-way sensitivity and variability analyses.

RESULTS

From a societal perspective, oseltamivir was cost-effective across all populations modeled, with an incremental cost per quality-adjusted life-year gained of $5,388, $6,317, $7,652, and $16,176 for high-risk adults, children, elderly adults, and healthy adults, respectively. Results were similar from a payer perspective. When indirect costs were included (for all populations except elderly adults), oseltamivir was cost saving. In sensitivity analyses, oseltamivir remained cost-effective across all patient populations for all values tested, except the probability of developing influenza-related pneumonia. Variability analyses showed that oseltamivir remained cost-effective under most scenarios tested.

CONCLUSION

Base-case results and sensitivity analyses from a decision-analysis model found that treatment of ILI with oseltamivir was cost-effective compared with usual care from U.S. payer and societal perspectives in all patient populations studied when only direct costs were considered.

Cost-effectiveness of live-attenuated influenza vaccine, trivalent in preventing influenza in young children attending day-care centres

Vaccinating children at day-care may be a cost-effective approach for improving influenza immunization rates in this high-risk group. This study uses influenza attack-rate data from a randomized, blinded, placebo-controlled clinical trial of live-attenuated influenza vaccine, trivalent in day-care centres from two consecutive influenza seasons, one with a moderate attack rate (H1N1 dominant) and one with a high attack rate (H3N2 dominant). Costs were measured in US dollars. In the moderate attack-rate season (vaccinated, 2.2%; placebo, 13.4%), vaccination saved US$ 5.47 per child in societal costs. In the high attack-rate season (vaccinated, 4.7%; placebo, 32.1%), vaccination led to a societal costs savings of US$ 144.44 per child.

Cost-effectiveness of universal influenza vaccination in a pregnant population

OBJECTIVE

The purpose of this study was to estimate whether universal influenza vaccination of pregnant women was cost-effective in the management of influenza-like illness during influenza season.

METHODS

A decision analysis model was developed to investigate the cost-effectiveness of providing inactivated trivalent influenza vaccine to all pregnant women. This scenario was compared with providing supportive care only on a case-by-case basis to the unvaccinated pregnant population.

RESULTS

Vaccination of 100% of pregnant women would save approximately 50 dollars per woman, resulting in a net gain of approximately 45 quality-adjusted hours relative to providing supportive care only.

CONCLUSION

Universal vaccination with inactivated trivalent influenza vaccine is cost-saving relative to providing supportive care alone in the pregnant population.

LEVEL OF EVIDENCE

III.

Evaluación de la eficiencia de la vacunación antigripal en la población laboral española

INTRODUCTION

Influenza is a major cause of morbidity and mortality worldwide. Currently, licensed influenza vaccines are safe and effective. Any intervention aimed at reducing the burden of illness is worth analyzing from a clinical and economic perspective.

OBJECTIVE

To assess the costs and benefits of an influenza vaccination program in the Spanish working population.

METHODS

A theoretical model of costs and benefits in terms of productivity savings was developed to compare 2 strategies (vaccination and non-vaccination) in 2 cohorts of 1,000 workers each. The time horizon was 1 year and the study's perspective was societal.

MAIN OUTCOME MEASURES

epidemiological and clinical data on the incidence of influenza and the effectiveness of the vaccine. Data on the use of direct and indirect resources were obtained from an expert panel of 5 experts in preventive medicine, microbiology, occupational health, and health economics. Unit costs (euros 2003) were extracted from local databases. A sensitivity analysis was performed with the data on incidence, effectiveness, and work absenteeism due to influenza.

RESULTS

In the base case scenario, influenza vaccine saved 35 Euros per worker, of which 88% were savings in work loss days avoided. Threshold values in the sensitivity analysis were 6% for the incidence of influenza and 1.5 days for absence from work, above which the vaccine leads to net savings.

CONCLUSIONS

Influenza vaccination in the Spanish working population might result in net resource savings to society at large.

Economic costs of influenza-related work absenteeism

BACKGROUND

Influenza vaccinations are currently advocated only for individuals over age 50. However, vaccination of all working-age people may be warranted based on reduced absenteeism from work.

OBJECTIVE

This study aims to quantify the association between lost workdays and influenza, controlling for other factors. A secondary aim of the study is to assess the net benefit of expanded vaccination in a workplace setting.

RESEARCH DESIGN

Multivariate regression analyses of the 1996 Medical Expenditure Panel Survey Household Component are used to estimate the number of workdays missed because of influenza-like illness (ILI) when controlling for other health, demographic, and employment factors. Mean productivity costs are measured in terms of absences from work and valued in dollar terms. The net benefit of influenza vaccination is estimated using a simple decision analysis.

SUBJECTS AND MEASURES

Health, demographic, and employment data for employed individuals between the ages of 22 and 64 years are analyzed.

RESULTS

The average number of workdays missed due to ILI was 1.30 days, and the average work loss was valued at 137 US dollars per person. The vaccine strategy was not preferred in the baseline analysis; however, this result was sensitive to assumptions regarding the incidence of influenza, the cost of delivering the vaccine, and the productivity impact of worker absenteeism. Moreover, nonproductivity benefits of vaccination were omitted.

CONCLUSIONS

The economic attractiveness of expanded investment in influenza vaccination hinges on employer- and population-specific assumptions. Our analysis provides a simple framework within which competing considerations of disease epidemiology, worker productivity, and economic cost may be weighed.

Cost-effectiveness of vaccination versus treatment of influenza in healthy adolescents and adults

At present time, there is uncertainty regarding whether influenza-like illness in healthy adults is best managed by preventive efforts that use the trivalent influenza vaccine, administration of neuraminidase inhibitors at the onset of illness, or recommendation of supportive care alone at the onset of illness. We conducted a cost-effectiveness analysis that examined these 3 strategies for managing influenza-like illness. Vaccination with inactivated trivalent vaccine would save approximately 25 dollars per person while resulting in a net gain of approximately 3.2 quality-adjusted hours relative to providing treatment with the neuraminidase inhibitor oseltamivir. A quality-adjusted hour is a fraction of a quality-adjusted life-year, which is the equivalent of 1 year lived in perfect health. Treatment with oseltamivir was associated with an incremental cost-effectiveness of approximately 27,619 dollars per quality-adjusted life-year gained relative to providing supportive care. Vaccination is cost-saving relative to providing either treatment with oseltamivir or providing supportive care alone.

Neuraminidase inhibitors: zanamivir and oseltamivir

OBJECTIVE

To review the pharmacology, pharmacokinetics, efficacy, and safety of zanamivir and oseltamivir for the prophylaxis and treatment of influenza.

DATA SOURCES

A MEDLINE search restricted to English-language journals was conducted (1980-May 2000).

STUDY SELECTION AND DATA EXTRACTION

All efficacy and safety trials were included if conducted in humans and published in a journal. Abstracts were included if no other data source was available.

DATA SYNTHESIS

Zanamivir and oseltamivir block influenza neuraminidase and prevent the cleavage of sialic acid residues, thus interfering with progeny virus dispersement within the mucosal secretions and reducing viral infectivity. The neuraminidase trials for prophylaxis and treatment of influenza enrolled predominantly young (mean age 29-37 y), healthy, mostly unvaccinated individuals who were at the lowest risk of influenza and its complications. When zanamivir 10 mg inhaled twice daily or oseltamivir 75 mg orally twice daily were used for treatment, systemic symptoms such as myalgias, fever, and headache were reduced by approximately 0.7-1.5 days. Greater efficacy (symptom reduction by 1.5-2.0 d) was noted in proven cases of influenza infection, in febrile patients, and in patients who received the treatment medication within 30 hours of symptom onset. Clinical efficacy did not increase when doses higher than the treatment dose approved by the Food and Drug Administration were used. When given for prophylaxis, zanamivir 10 mg inhaled once daily or oseltamivir 75 mg orally once daily was used for four to six weeks and achieved protective clinical efficacy for laboratory-confirmed influenza ranging from 67% to 74%, depending on whether culture or serologic tests were performed. The most common adverse effects (usually < 5%) included upper respiratory tract symptoms. Patients with asthma or chronic obstructive pulmonary disease who received zanamivir had an increased incidence of a > 20% decline in forced expiratory volume in one second or peak expiratory flow rates. Headaches, nausea, and vomiting were more frequent in the oseltamivir groups than in placebo groups. The most common gastrointestinal adverse effects, nausea and vomiting, were reduced to approximately 10% by administering the medication with food.

CONCLUSIONS

Zanamivir and oseltamivir are more effective in preventing culture-positive influenza or for treatment of culture-positive influenza in febrile (> or = 37.8 degrees C) individuals. Treatment is more effective if initiated within 30 hours of symptom onset in febrile individuals; however, it is difficult to meet these criteria. More realistically, clinical efficacy is closer to 60-70% and, for treatment started within 48 hours for laboratory-confirmed influenza, symptom reduction is approximately 0.7-1.5 days. If used appropriately to minimize the development of resistance, the neuraminidase inhibitors represent a new and unique class of antiinfluenza agents that can potentially reduce the morbidity associated with influenza.