Cost-Effectiveness of Defending against Bioterrorism: A Comparison of Vaccination and Antibiotic Prophylaxis against Anthrax

19 April 2005 | Volume 142 Issue 8 | Pages 601-610

Background: Weaponized Bacillus anthracis is one of the few biological agents that can cause death and disease in sufficient numbers to devastate an urban setting.

Objective: To evaluate the cost-effectiveness of strategies for prophylaxis and treatment of an aerosolized B. anthracis bioterror attack.

Design: Decision analytic model.

Data Sources: We derived probabilities of anthrax exposure, vaccine and treatment characteristics, and their costs and associated clinical outcomes from the medical literature and bioterrorism-preparedness experts.

Target Population: Persons living and working in a large metropolitan U.S. city.

Time Horizon: Patient lifetime.

Perspective: Societal.

Intervention: We evaluated 4 postattack strategies: no prophylaxis, vaccination alone, antibiotic prophylaxis alone, or vaccination and antibiotic prophylaxis, as well as preattack vaccination versus no vaccination.

Outcome Measures: Costs, quality-adjusted life-years, life-years, and incremental cost-effectiveness.

Results of Base-Case Analysis: If an aerosolized B. anthracis bioweapon attack occurs, postexposure prophylactic vaccination and antibiotic therapy for those potentially exposed is the most effective (0.33 life-year gained per person) and least costly ($355 saved per person) strategy, as compared with vaccination alone. At low baseline probabilities of attack and exposure, mass previous vaccination of a metropolitan population is more costly ($815 million for a city of 5 million people) and not more effective than no vaccination.

Results of Sensitivity Analysis: If prophylactic antibiotics cannot be promptly distributed after exposure, previous vaccination may become cost-effective.

Limitations: The probability of exposure and disease critically depends on the probability and mechanism of bioweapon release.

Conclusions: In the event of an aerosolized B. anthracis bioweapon attack over an unvaccinated metropolitan U.S. population, postattack prophylactic vaccination and antibiotic therapy is the most effective and least expensive strategy.

Editors' Notes Context The best strategies for preventing infection in the event of bioterrorism with aerosolized Bacillus anthracis are unknown. Given the paucity of data, the development of strategies must rely heavily on hypothetical models. Contribution This decision model evaluated postattack strategies (no prophylaxis, vaccination alone, antibiotic prophylaxis alone, or both plus preattack vaccination) and identified postexposure vaccination and antibiotics as the most effective and least expensive strategy. Mass preattack vaccination did not seem cost-effective. Cautions The model is based on many assumptions, and the results depend heavily on probabilities that are difficult to estimate, such as the probability of an attack. –The Editors

 

Author and Article Information

From Sunnybrook and Women's College Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada; Duke University, Duke Clinical Research Institute, Durham, North Carolina; and Veterans Affairs Palo Alto Health Care System, Center for Primary Care and Outcomes Research, Stanford University, Stanford, California.

Acknowledgments: The authors thank Sara H. Cody, MD; David S. Stephens, MD; Christine H. Lee, MD; Ellen Jo Baron, PhD; Eva E. Shimaoka, MD; Justin Graham, MD; Michael K. Gould, MD, MS; Peter W. Groeneveld, MD, MS; and the CDC Public Service Response for their helpful input into the content and structure of the decision model.

Grant Support: By the University of Toronto and Sunnybrook and Women's College Health Sciences Centre (Dr. Fowler) and the Laughlin Fund (Dr. Garber).

Potential Financial Conflicts of Interest: Grants received: D.M. Bravata (Agency for Healthcare Research and Quality).

Requests for Single Reprints: Robert A. Fowler, MD, MS, Sunnybrook and Women's College Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, Room D478, Toronto, Ontario M4N 3M5, Canada; e-mail, rob.fowler{at}sw.ca.

Current Author Addresses: Dr. Fowler: Departments of Medicine and Critical Care Medicine, Sunnybrook and Women's College Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, Room D478, Toronto, Ontario, M4N 3M5 Canada.

Dr. Sanders: Duke University, Duke Clinical Research Institute, PO Box 17969, Durham, NC 27715.

Drs. Bravata and Nouri: Center for Primary Care and Outcomes Research, 117 Encina Commons, Stanford University, Stanford, CA 94305-6019.

Mr. Gastwirth, Mr. Peterson, and Ms. Broker: Graduate School of Business, Stanford University, 518 Memorial Way, Stanford, CA 94305-5015.

Drs. Garber and Owens: Department of Veterans Affairs Palo Alto Health Care System and Center for Primary Care and Outcomes Research, 117 Encina Commons, Stanford University, Stanford, CA 94305-6019.

Author Contributions: Conception and design: R.A. Fowler, G.D. Sanders, D.M. Bravata, B. Nouri, J.M Gastwirth, D. Peterson, A.G. Broker, A.M. Garber, D.K. Owens.

Analysis and interpretation of the data: R.A. Fowler, G.D. Sanders, D.M. Bravata, B. Nouri, J.M Gastwirth, D. Peterson, A.G. Broker, A.M. Garber, D.K. Owens.

Drafting of the article: R.A. Fowler, G.D. Sanders, D.M. Bravata, J.M Gastwirth, B. Nouri, D. Peterson, A.G. Broker, A.M. Garber, D.K. Owens.

Critical revision of the article for important intellectual content: R.A. Fowler, G.D. Sanders, D.M. Bravata, A.M. Garber, D.K. Owens.

Final approval of the article: R.A. Fowler, D.M. Bravata, A.M. Garber, D.K. Owens.

Statistical expertise: R.A. Fowler, G.D. Sanders, D.M. Bravata, A.M. Garber, D.K. Owens.

Administrative, technical, or logistic support: R.A. Fowler.

Collection and assembly of data: R.A. Fowler, J.M Gastwirth, D. Peterson, B. Nouri, A.G. Broker, G.D. Sanders, D.M. Bravata, D.K. Owens.

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Annals Online, 26 Apr 2005 [Full text]