Rationale:

• Postexposure antibiotic prophylaxis prevents inhalational anthrax.
• Postexposure ciprofloxacin appears to be protective in humans.
• B. anthracis may be resistant to doxycycline and β-lactams.
• B. anthracis spores, which are dormant and do not cause active infection, can germinate weeks to months after exposure and cause inhalational anthrax.
• Vaccination against anthrax may prevent disease from the remaining spores once antibiotic prophylaxis is discontinued.
• Anthrax vaccine is safe, but side effects occur.

Evidence:

• Rhesus monkeys exposed to inhaled anthrax (~8 LD₅₀) and then given postexposure penicillin, doxycycline, or ciprofloxacin had a significantly better survival rate than monkeys given no antibiotic or those only given vaccine (13).
• Rhesus monkeys exposed to large doses of inhaled anthrax spores and then given ciprofloxacin for 14 days and three doses of postexposure vaccine had a significantly greater survival rate than monkeys given only ciprofloxacin for 14 days (14).
• No person in a high-risk group who was given ciprofloxacin during the 2001 anthrax attack has so far developed inhalational anthrax (15).
• B. anthracis strains resistant to penicillin and tetracycline have been engineered (16).
• Anthrax spores were noted in the lung parenchyma of experimentally infected rhesus monkeys for up to 100 days (17).
• The last case of inhalational anthrax during the 1979 Sverdlovsk outbreak was 43 days after exposure (18).
• Animal and human studies support the efficacy of anthrax vaccine for prevention of inhalational and cutaneous anthrax (1; 2; 3; 4).
• Mild cutaneous reactions occur in 20% of patients vaccinated, whereas severe local reactions and systemic reactions occur in 1% (1; 8; 9).
• Data collected during a postexposure antiobiotic prophylaxis campaign showed that adherence to a full 60-day course of antibiotic therapy was only approximately 44%. Poor adherence was not necessarily related to adverse events (19).
• A cost-effectiveness analysis showed that postexposure antibiotic therapy combined with vaccination would be the most effective and least costly strategy for prophylaxis and treatment of patients in the event of a bioterror attack with anthrax (20).

Comments:

• None.