Lessons learned from the CDC's post‐exposure prophylaxis program following the anthrax attacks of 2001

The bioterrorism-related outbreak of anthrax in Fall 2001 was the result of unprecedented attacks on residents of the United States. Although addressees of anthrax spore-filled letters were most likely the targets of the attacks, thousands of U.S. postal employees and others were exposed through aerosolization of spores in mail processing facilities. 1 These attacks precipitated decisions to recommend post-exposure prophylaxis (PEP) to an estimated 10 000 individuals potentially exposed to Bacillus anthracis to prevent inhalational anthrax. 2 Initially, the Centers for Disease Control and Prevention (CDC) recommended 60 days of antimicrobial PEP (initial PEP program), mainly either doxycycline or ciprofloxacin. 2 The CDC eventually extended its recommendation to 40 additional days of antimicrobial prophylaxis with or without three doses of anthrax vaccine adsorbed (AVA) under an investigational new drug (IND) protocol (extended PEP program). 3 Overall, approximately 5420 individuals received education about the extended PEP program. Of these, 1727 individuals agreed to take antibiotics for a full 100 days, but only 199 also chose to be vaccinated with AVA. 4,5 Fifty-seven percent of those who took at least one dose of antimicrobial prophylaxis during the first 60 days of PEP sustained an adverse event (AE), of which less than 1% were considered serious. 6 No deaths were attributed to PEP. Of the thousands of exposed individuals who were advised to take PEP, none developed any form of anthrax, whether or not they