Purpose: The CDC's Anthrax Vaccine and Antibiotic Availability Program was implemented under an Investigational New Drug (IND) application to provide additional post-exposure prophylaxis for individuals potentially exposed to Bacillus anthracis in the fall of 2001. Participants were provided with two options: (1) 40 additional days of antimicrobial prophylaxis (i.e., ciprofloxacin, doxycycline, or amoxicillin); or (2) 40 additional days of antimicrobial prophylaxis plus three doses of anthrax vaccine adsorbed (AVA).

Methods: Participants were monitored for adverse events (AEs). Participants were asked to complete 2-week AE diaries for 6 weeks post-enrollment, and approximately 2 months after enrollment, active surveillance was conducted through telephone interviews with 1113 (64%) participants.

Results: A total of 1727 of approximately 10 000 previously prophylaxed persons enrolled to receive 40 additional days of antibiotics. Of these, 199 opted at enrollment to receive three doses of AVA in addition to the additional 40 days of antibiotic. Overall, 28% of participants reported at least one AE on their diaries. Results varied by surveillance mechanism, the diary data indicated differences in the proportion reporting AEs between participants receiving antibiotic only and participants receiving antibiotic and AVA. However, during the active 2-month telephone follow-up, the rates of AEs reported for both the antibiotic only and antibiotic plus AVA treatment regimens were similar. Additionally, ciprofloxacin and doxycycline had similar AE profiles, with only rigors reported significantly more often among ciprofloxacin recipients.

Conclusions: Overall, the rates of AEs experienced by all participants were acceptable given the seriousness of potential B. anthracis exposure.