The CDC issued updated guidelines for the use of the anthrax vaccine in 2010. In their updated report, the CDC decreased the recommended primary doses from 6 to 5 (0, 4 weeks, 6 months, 12 months, 18 months) for pre-exposure prophylaxis and advised that the vaccine be administered intramuscularly (IM). Annual booster doses were also recommended. For post-exposure, three doses are given subcutaneously at 0, 2, and 4 weeks in conjunction with 60 days of antibiotic treatment were recommended.
The CDC also stated that while pre-exposure vaccination of pregnant women was not recommended if a risk of inhalation anthrax existed, pregnant women should be given three vaccine doses (0, 2, and 4 weeks) and 60 days of antibiotics. This recommendation was made even though the vaccine package insert states that Biothrax anthrax vaccine is a Pregnancy Category D vaccine and demonstrated there was evidence of harm in human studies or fetal risk had been shown in pre- or post-marketing surveillance data. Nursing mothers were also recommended the vaccine pre- and post-exposure, even though it is unknown whether it can be transmitted to infants through human milk.
In 2011, the National Biodefense Science Board (NBSB) recommended that the anthrax vaccine be studied in children before an attack, pending a review of the ethical issues. After over a year of meetings and deliberations, the Presidential Commission for the Study of Bioethical Issues recommended that no anthrax vaccine studies be completed on children until studies could confirm that children would not face anything more than minimal risk.
In January 2020, the CDC updated its guidance on anthrax vaccination. It recommended that for pre-exposure prophylaxis, a 3-dose primary series (0, 1, and 6 months) and an initial 2-dose booster series (12 and 18 months) be administered intramuscularly. A yearly booster dose was recommended for persons considered high risk (lab workers handling anthrax, members of the military). The CDC recommends a booster dose every three years for persons who have completed the initial five doses and are not considered high risk but would like to maintain vaccine acquired protection.
For post-exposure prophylaxis, the CDC recommended that persons with known or suspected anthrax exposure be administered three vaccine doses subcutaneously (SC) (0, 1, and 4 weeks) in conjunction with antibiotic therapy.
In July 2023, the FDA approved the use of CYFENDUS, an anthrax vaccine specifically for post-exposure prophylaxis. This vaccine uses the CpG 7909 adjuvant to bind to the Toll-like receptor 9 to enhance the body’s immune response to the anthrax antigen.
Cytosine phosphoguanine (CpG) is a synthetic form of DNA that mimics viral and bacterial genetic material. Only one FDA-approved vaccine, Heplisav-B Hepatitis B vaccine, uses a CpG adjuvant – CpG 1018. The FDA twice rejected licensing of Heplisav-B due to outstanding safety concerns. In 2013, the FDA rejected the vaccine due to concerns that this adjuvant could trigger autoimmune disorders. It was rejected again in November 2016 due to concerns about cardiovascular events and deaths. One year later, in November 2017, the FDA approved the vaccine despite unresolved safety concerns. In pre-licensing clinical trials, those who received Heplisav-B had a 7-times higher risk of heart attack than those receiving the control vaccine, Engerix-B hepatitis B vaccine.
Clinical trials to determine the efficacy of CYFENDUS were based on animal studies, and findings were used to predict the efficacy in humans. Animal studies were also conducted in guinea pigs to determine whether CYFENDUS improved survival rates after the recommended antibiotics were completed compared to treatment with only antibiotics. According to the manufacturer, CYFENDUS increased survivor rates in guinea pigs in the 21 days after completion of antibiotics.
CYFENDUS is FDA approved to be administered by intramuscular injection to persons between 18 and 65 years of age with known or suspected anthrax exposure as a 2-dose series (0 and 2 weeks) in conjunction with antibiotics.
IMPORTANT NOTE: NVIC “Quick Facts” is not a substitute for becoming fully informed about anthrax and the anthrax vaccine. NVIC recommends consumers read comprehensive information NVIC provides on anthrax, the vaccine manufacturer product information inserts, and speak with one or more trusted health care professionals before making a vaccination decision for yourself or your child.
