Anthrax

Prophylaxis

Vaccine: A licensed vaccine (Anthrax Vaccine Adsorbed (AVA) Bioport, Lansing, MI) is derived from sterile culture fluid supernatant taken from an attenuated (non-encapsulated) strain. Therefore, the vaccine does not contain live or dead organisms. The vaccination series consists of six 0.5-ml subcutaneous doses at 0, 2, and 4 weeks; then 6, 12, and 18 months, followed by yearly boosters. Current Department of Defense policy for missed doses (for those individuals required to remain immune) is to administer the missed dose ASAP and reset the timeline for the series based upon the most recent dose. The Food and Drug Administration (FDA) further clarified in December, 2003 that AVA "is safe and effective for the prevention of anthrax disease - regardless of the route of exposure." AVA is licensed only for preexposure prophylaxis of anthrax in adults. It is available for preexposure use in children, and postexposure prophylaxis (PEP) in adults and children only under INDs through the CDC and DoD. As with all vaccines, the degree of protection depends upon the magnitude of the challenge dose; vaccine-induced protection could presumably be overwhelmed by extremely high spore challenge. Thus, even fully immune personnel should receive antibiotic prophylaxis if exposed to aerosolized anthrax, per the guidelines given below.

Contraindications for use of this vaccine include hypersensitivity reaction to a previous dose of vaccine and age < 18 or > 65. Reasons for temporary deferment of the vaccine include pregnancy, active infection with fever, or a course of immune-suppressing drugs such as steroids. Reactogenicity is mild to moderate. Up to 30 percent of recipients may experience mild discomfort at the inoculation site for up to 72 hr (e.g., tenderness, erythema, edema, pruritus), fewer experience moderate reactions, while less than 1 percent may experience more severe local reactions, potentially limiting use of the arm for 1-2 days. Modest systemic reactions (e.g., myalgia, malaise, low-grade fever) are uncommon, and severe systemic reactions such as anaphylaxis, which precludes additional vaccination, are rare. The vaccine should be stored between 2-6oC (refrigerator temperature, not frozen).

Current DoD policy is to require AVA vaccination for active duty personnel (without specific contraindications) as well as some emergency-essential DoD civilians and contractors to deploy for more than 15 consecutive days or more than 15 cumulative days over 12 months in designated "higher-threat" areas. The vaccination series should be initiated, when feasible, at least 45 days before deployment. DoD has continued to make vaccine available to special mission units, manufacturing and DoD lab workers, and congressionally-mandated anthrax vaccine researchers. Details of the DoD (and service specific guidance) can be found at http://www.anthrax.osd.mil/resource/policies/policies.asp.

Some AVA has been made available to U.S. Department of Health and Human Services (HHS). In 2002 the Advisory Committee on Immunization Practices (ACIP) recommended that HHS prioritize AVA availability to personnel at risk for repeated occupational exposure to anthrax spores, including workers handling environmental specimens (especially powders) and performing confirmatory testing for anthrax in Reference and National labs in the U.S. Laboratory Response Network (LRN), and emergency response personnel who may have to enter anthrax spore-contaminated areas repeatedly.

Antibiotics: No antibiotics are approved for preexposure prophylaxis of anthrax spores. Thus, official DoD policy is not to initiate prophylactic antibiotics until AFTER an attack is suspected to have occurred. After a suspected exposure to aerosolized anthrax spores of unknown antibiotic susceptibility, prophylaxis with ciprofloxacin (500 mg po bid for adults, and 10-15 mg/kg po bid (up to 1 g/day) for children) OR doxycycline (100 mg po bid for adults or children >8 yr and >45 kg, and 2.2 mg/kg po bid (up to 200 mg/day) for children < 8yr) should be initiated immediately. Should an attack be confirmed as anthrax, antibiotics should be continued for variable lengths of time dependent upon the patient's anthrax immune status and suspected inhaled dose of anthrax. If antibiotic susceptibilities allow, patients who cannot tolerate tetracyclines or quinolone antibiotics can be switched to amoxicillin (500 mg po tid for adults and 80 mg/kg divided tid (>= 1.5 g/day) in children). The DoD position is that vaccination with AVA is a critical part of postexposure prophylaxis for inhaled anthrax; without vaccine, victims exposed to inhaled anthrax spores are unlikely to develop the immunity necessary to prevent anthrax disease caused by spores that germinate after antibiotics are discontinued. Recently the ACIP agreed that AVA should be made available as an IND to civilians as a part of PEP of inhalational anthrax as well (MMWR, 51(45);1024-26, 15 Nov 2002) Patients who were fully immune* before the attack should continue antibiotics for at least 30 days. If vaccine is available, previously unvaccinated patients should receive at least three doses of AVA at 2-week intervals, and then continue antibiotics for at least 1-2 weeks after receipt of the third dose of AVA. If the vaccine is not available or the patient cannot receive the vaccine for some other reason, antibiotics should be continued for at least 60 days. Upon discontinuation of antibiotics, patients should be closely observed. If clinical signs of anthrax occur, empiric therapy for anthrax is indicated, pending etiologic diagnosis. Optimally, patients should have medical care available upon discontinuation of antibiotics from a fixed medical care facility with intensive care capabilities and infectious disease consultants.

* Vaccinated = completed six doses of AVA and up-to-date on boosters, or minimum of three doses within past 6 months. Those who have already received three doses within 6 months of exposure should continue with their routine vaccine schedule.

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