Cost-effectiveness of defending against bioterrorism: a comparison of vaccination and antibiotic prophylaxis against anthrax

Abstract

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 dollars 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 dollars 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.