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

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.