Updated Recommendations on the Use of Anthrax Vaccine in the United States

Updates to the 2009 recommendations from the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices (ACIP) regarding the use of the anthrax vaccine in the United States were published in the Morbidity and Mortality Weekly Report.

The anthrax vaccine adsorbed is licensed for pre-exposure prophylaxis, (PrEP) as well as postexposure prophylaxis (PEP), for adults (aged 18-65 years) at high risk for exposure to Bacillis anthracis. There is also a second-generation anthrax vaccine named AV7909, which is currently in phase 3 trials for use in PEP.

The recommended changes to the 2009 recommendations included a booster dose of anthrax vaccine adsorbed for PrEP every 3 years, rather than annually, in those not at risk for exposure who want to maintain protection and who previously received the initial anthrax vaccine adsorbed 3-dose priming and 2-dose booster series. Furthermore, during large-scale emergency responses, the adsorbed anthrax vaccine for PEP can be administered intramuscularly if the subcutaneous route poses significant material, personnel, or clinical challenges that could delay or preclude vaccination. However, the subcutaneous route continues to be the preferred route for PEP in other circumstances. The report also includes new recommendations on dose-sparing vaccine PEP regimes if vaccine supply is insufficient for all potentially exposed persons and clarifications on the durations of antimicrobial therapy when used in conjunction with vaccine PEP.

These updated recommendations were made for use by clinicians and to guide emergency preparedness officials and planners in providing the vaccine in situations such as a wide-area aerosol release of B anthracis spores. Furthermore, the dose-sparing recommendations can be used to increase the numbers of individuals receiving PEP in a mass casualty event.

Investigators further recommended that assessments of immunogenicity and safety in populations, such as children, older adults, and pregnant and nursing mothers, are required. Similarly, additional evaluations of the dose-sparing schedules, the interchangeability of anthrax vaccine adsorbed and AV7909 and testing of their stability outside of the cold chain. Future work should also focus on determining the optimal booster schedule to provide long-term protection after receiving the PEP vaccine schedule, assessments of whether co-administration of obiltoxaximab with AVA impairs vaccine immunogenicity, and the optimal duration of antimicrobial use in postexposure settings.

Recommendations will be further updated by the Advisory Committee on Immunization Practices Anthrax Vaccines Work Group after the approval of AV7909 as a licensed vaccine and review of the additional data leading to its licensure.

Reference

Bower WA, Schiffer J, Atmar RL, et al. Use of anthrax vaccine in the United States: Recommendations of the Advisory Committee on Immunization Practices, 2019. MMWR Recomm Rep. 2019;68:1-14.