BACKGROUND/RATIONALE:
In 2001 a small-scale bioterrorism-related anthrax attack was perpetrated via the mail. Although exposure was limited, the attack caused generalized panic and social disruption. The VA, because of its potential vulnerability to a postal attack directed at government facilities and because of its participation in national emergencies, has an interest in identifying the optimal response to both small-scale and large-scale bioterrorism attacks.
OBJECTIVE(S):
Using a willingness-to-pay threshold of $100,000 per quality adjusted life year (QALY), a cost-effectiveness analysis was conducted comparing several potential response strategies to a small scale anthrax attack scenario as well as to a mass inhalational anthrax attack scenario. The optimal response for each scenario was determined.
METHODS:
For the small scale attack we used a decision analytic model to compare three basic response strategies from a societal perspective: 1) pre-attack vaccination; 2) post-attack antibiotics alone; and 3) post-attack antibiotics + post-attack vaccination. We used Markov modeling to represent the potential events following vaccination and anthrax exposure. The outcomes included costs, quality adjusted life years, and incremental cost-effectiveness. We extended this approach to evaluate the optimal response to a mass inhalational anthrax attack. We examined two additional response options: 1) pre-attack vaccination combined with post-attack antibiotics; and 2) pre-attack vaccination followed by post-attack antibiotics combined with post-attack vaccination. Further, in the mass attack model we explored the timeliness of each response and the relationship of timing to optimal outcome. In preparation for modeling both scenarios, we conducted a systematic review of all the published literature that modeled potential responses to an anthrax attack.
FINDINGS/RESULTS:
Our base case-analysis for the small-scale attack indicates that post-attack administration of antibiotics is the least costly strategy, and post-attack antibiotic and post-attack vaccination strategy is the most effective, both in terms of expected number of deaths and overall QALYs. The incremental cost-effectiveness rate (ICER) of post-attack antibiotic combined with post-attack vaccination relative to post-attack antibiotics alone is $59,558 per QALY. Pre-attack vaccination is the least effective (assuming partial adherence) and the most costly strategy. Even if a pre-attack vaccination program entirely prevents any anthrax attack on the postal service, pre-attack vaccination costs almost $17,000,000 per QALY relative to post-attack antibiotics alone. Sensitivity analyses indicate that post-attack antibiotic and post-attack vaccination is cost-effective relative to post-attack antibiotic over the full range of most model parameters. Post-attack antibiotic is optimal only when the proportion of people dying from an anthrax attack approaches zero. Pre-attack vaccination becomes preferable to post-attack antibiotics alone only when probability of anthrax exposure is ≥ 16%--a level of exposure much higher than observed in the 2001 attack. The analysis of the large-scale mass attack scenario and the systematic review are almost complete.
IMPACT:
Cost-effective strategies for responding to a small-scale anthrax attack against a postal facility depend on the assumed infection rates and vaccination costs. Our study informs administrators and policy makers on the cost-effectiveness of various medical responses to a small-scale anthrax attack directed at a government building, using a postal facility as our model target. Post-attack vaccination and antibiotic treatment of exposed personnel appears to be the optimal response to a future small-scale bioterrorist anthrax attack perpetrated through the mail. We speculate that individual non-adherence to immunization and the limited advantage of additional vaccination over post-exposure antibiotics alone may prompt administrators and policy makers to select the use of antibiotics alone as a reasonable response strategy. The ultimate purpose of a CEA is to optimize the use of limited resources within a system, and the VA system is one that is likely to deal with the effects of anthrax threat or dissemination.
PUBLICATIONS:
Journal Articles
- Schmitt B, Dobrez D, Parada JP, Kyriacou DN, Golub RM, Sharma R, Bennett C. Responding to a small-scale bioterrorist anthrax attack: cost-effectiveness analysis comparing preattack vaccination with postattack antibiotic treatment and vaccination. Annals of Internal Medicine. 2007; 167(7): 655-62.
- Kyriacou DN, Yarnold PR, Stein AC, Schmitt BP, Soltysik RC, Nelson RR, Frerichs RR, Noskin GA, Belknap SM, Bennett CL. Discriminating inhalational anthrax from community-acquired pneumonia using chest radiograph findings and a clinical algorithm. Chest. 2007; 131(2): 489-96.
- Parada JP. Smallpox and the United States smallpox vaccination program. Federal Practitioner. 2004; 21(5): 92-106.
