A recent report updates the 2009 recommendations from the CDC Advisory Committee on Immunization Practices (ACIP) regarding use of anthrax vaccine in the United States.

A key change from previous guidance, according to an article in the Morbidity & Mortality Weekly Report, is that a booster dose of anthrax vaccine adsorbed (AVA) for preexposure prophylaxis (PrEP) can be given every 3 years instead of annually to persons not at high risk for exposure to Bacillus anthracis. That applies to those who have previously received the initial AVA 3-dose priming and 2-dose booster series and want to maintain protection.

Another change is the recommendation that, during a large-scale emergency response, AVA for postexposure prophylaxis (PEP) can be administered using an IM route if the SC route of administration poses significant materiel, personnel, or clinical challenges that might delay or preclude vaccination.

The new report also makes recommendations on dose-sparing AVA PEP regimens if the anthrax vaccine supply is insufficient to vaccinate all potentially exposed persons and clarifies the duration of antimicrobial therapy when used in conjunction with vaccine for PEP.

“These updated recommendations can be used by health care providers and guide emergency preparedness officials and planners who are developing plans to provide anthrax vaccine, including preparations for a wide-area aerosol release of B. anthracis spores,” note researchers from the CDC. “The recommendations also provide guidance on dose-sparing options, if needed, to extend the supply of vaccine to increase the number of persons receiving PEP in a mass casualty event.”

AVA (BioThrax) is licensed for PrEP for adults aged 18 to 65 years at high risk for exposure to B anthracis. The FDA approved a dosage of 0.5 mL administered IM at 0, 1, and 6 months with boosters at 6 and 12 months after completion of the primary series and at 12-month intervals thereafter. 

AVA also is licensed for PEP in combination with antimicrobials for adults aged 18 to 65 years with suspected or known exposure to aerosolized B anthracis spores. The dosage approved by the  FDA is 0.5 mL administered SC at 0, 2, and 4 weeks. 

The CDC points out that, for those not included in the FDA-approved indication for PEP, AVA will be available for PEP use for children, pregnant women, nursing mothers, and adults aged 66 years and older under appropriate emergency-use regulatory provisions. 

“Although data are lacking on the immune impact of mixing the IM and SC routes of administration, as might occur when switching from PrEP to PEP, switching between routes would be unlikely to adversely impact immunity because both routes provide adequate immunity,” the authors suggest.

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