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What is the history of Anthrax vaccine use in America?

Updated December 29, 2023

The first vaccine for anthrax was developed in the late 19th century by Louis Pasteur for use in animals. This vaccine was believed to be a heat attenuated whole-cell vaccine; however, scientists now believe that the vaccine contained some bacteria that produced small amounts of the toxin. While considered effective at preventing anthrax in animals, it was also known to cause disease and death in some. In the late 1930s, Max Sterne developed a live-spore-containing vaccine for use in animals which largely replaced Pasteur’s vaccine. 

Anthrax vaccines for human use were first tested in the 1950s. Six hundred scientists were administered the vaccine at Fort Detrick, and the vaccine was declared safe for human use. After the initial testing, field studies were conducted on the vaccine’s safety and effectiveness among workers in industrial settings who were known to be at high risk for anthrax. This vaccine was supplied by Wright and Associates of the U.S. Army Chemical Corps of Fort Detrick.

Between 1950 and 1959, workers at four mills in the U.S. Northeast were allowed to participate in the study. Those who received the experimental vaccine were administered a product containing a modified version of the Vollum strain of B. anthracis, which included 0.1 percent aluminum potassium sulfate (alum). The control group received a “placebo” containing 0.1 percent alum. Participants were administered a primary vaccine series of 3 doses given at 2-week intervals and three additional booster doses beginning at six months given at 6-month intervals. 

During the study period, 26 cases of anthrax were reported, with four occurring in persons who were partially vaccinated and one in a person who was fully vaccinated. 

The trial participants were examined 24 and 48 hours after each vaccine dose for local or systemic reaction symptoms. Swelling, redness, and itching at the injection site were the most common symptoms reported after vaccination, with most symptoms resolving within two days. However, some vaccine recipients developed persistent nodules at the injection site, and others reported significant swelling. Most reactions occurred after the second and sixth vaccine dose. There were also reports of reactions among persons who received the aluminum-containing “placebo”; however, the symptoms were considered less severe than those who received the vaccine. Thirty-five percent of vaccine recipients reported localized adverse events following vaccination. 

Researchers reported that only two systemic reactions occurred among study participants, and these individuals also experienced injection site swelling. Both individuals reported malaise lasting about 24 hours after vaccination. Two study participants who were previously diagnosed with cutaneous anthrax were inadvertently administered the vaccine, and both experienced severe localized reactions, including swelling, redness, and itching. Neither individual received any additional vaccine doses. One person who had previously recovered from inhalation anthrax was administered at least one anthrax vaccine dose but did not report any side effects. 

Researchers reported that while the vaccine appeared to be protective against cutaneous anthrax, the data was inconclusive on whether protection would extend to inhalation anthrax. Additionally, they reported that the vaccine did not offer long-term protection, and three primary vaccine doses and a booster dose were needed to ensure protection against anthrax for at least six months. The vaccine was declared safe and effective based on this study published in 1962, which involved only 1,249 individuals. 

This early vaccine was initially manufactured by Merck Sharp & Dohme; however, the vaccine’s original license was granted to the Michigan Department of Public Health by the Division of Biologics of the National Institutes of Health because the FDA had not yet been established. 

For many years, the anthrax vaccine used by veterinarians, researchers, and those handling animal products that could be contaminated with anthrax bacteria, was manufactured by the Michigan Department of Health in a Lansing, Michigan lab. The vaccine manufacturing plant owned by the state had also been used for many years to manufacture and distribute DPT vaccines to Michigan state residents.  In 1995, the plant’s name was changed to Michigan Biologic Products Institute (MBPI). 

In the early 1990s, U.S. military personnel serving during Operation Desert Storm were administered anthrax vaccines due to concerns that Iraq had manufactured weapons capable of dispersing anthrax spores. 

Many military members who served during the Operation Desert Storm era reported significant health issues, including chronic fatigue syndrome, joint and muscle pain, rashes, dizziness, headaches, seizures, and autoimmune issues. These symptoms were eventually labeled Gulf War Syndrome and were found to affect both deployed and non-deployed troops. Additionally, many individuals experiencing these symptoms had anti-squalene antibodies (ASA) that were not present before anthrax vaccination. 

Several lots of anthrax vaccines were tested and found to contain squalene, but the source was unknown. While the FDA considered the levels of squalene in the vaccines to be too low to be capable of harm, researchers disagreed with this conclusion and expressed concerns that there were many unanswered questions. 

FDA inspections of the anthrax vaccine manufacturing plants in the 1990s revealed multiple deficiencies that were not promptly corrected. These deficiencies were believed to impact both the efficacy and safety of the vaccine lots. As a result, vaccine production was halted until problems were adequately addressed. 

Despite issues regarding the manufacturing of the anthrax vaccine, Defense Secretary William Cohen ordered mandatory anthrax vaccination for all military personnel in 1997. 

In 1998, BioPort Corporation, headed by U.S. Admiral William J. Crowe, Jr. (now deceased) and international business entrepreneur Fuad El-Hibri, purchased the Michigan vaccine lab. Anthrax vaccine manufacturing was taken over by BioPort Corporation when they bought the Michigan state plant, made modifications, and geared up to meet the Pentagon’s goal of vaccinating all 2.4 million active-duty and reserve troops with anthrax vaccine.  However, BioPort failed FDA quality control inspection several times, which resulted in the interruption of anthrax vaccine supplies and the use of the vaccine by the military. 

In the late 1990s and early 2000s, Congressional hearings were held in the U.S. House of Representatives Government Reform Committee on anthrax vaccine safety, efficacy, and lack of informed consent protections in the military’s mandatory anthrax vaccination policies. Testimony from vaccine-injured military veterans included several hundred cases where career soldiers chose to face court-martial rather than agree to be vaccinated or revaccinated with anthrax vaccine after experiencing serious reactions.  

The CDC’s Advisory Committee on Immunization Practices (ACIP) issued guidelines for anthrax vaccine use in 2000 and recommended the vaccine for laboratory workers who had frequent contact with anthrax spores, persons handling animals and animal byproducts in an environment that might place them at risk of exposure, and military personnel. ACIP reported that the vaccine’s manufacturer recommended three primary doses at 0, 2, and 4 weeks subcutaneously, followed by three booster doses at 6, 12, and 18 months, and annual boosters thereafter; however, ACIP also reported that the rationale for this schedule was not known. 

Injection site reactions were associated with vaccination, but studies on chronic illness following vaccination were lacking. There was also insufficient data to support or reject an association between long-term health effects and vaccination. ACIP stated that further studies by the Department of Defense on the vaccine were underway.  

In 2001, a bioterrorism attack caused 22 individuals to develop anthrax (11 inhalation and 11 cutaneous) after envelopes containing anthrax spores were mailed to various U.S. government officials and news media outlets. Twenty of the 22 cases were linked to handling mail items, and five people died as a result. 

Following the 2001 bioterrorism attacks involving postal and Capitol workers, federal health officials with Health and Human Services (HHS) announced that anthrax vaccines would be made available to persons who may have been exposed to anthrax. The use of the anthrax vaccine post-exposure was considered experimental because the vaccine was not approved for post-exposure prophylaxis. HHS stated that they were offering the vaccine but not making a recommendation due to the risk of vaccine reactions and the lack of data to support the vaccine’s use post-exposure. 

The anthrax vaccine given to military personnel and civilians after Sept. 11, 2001, had never received final FDA approval for effectiveness in preventing anthrax inhalation infections, which is theoretically how the organism would be turned into a bioterrorism weapon. Thus, Biothrax vaccine continued to be classified as experimental. 

In 2002, Congress's General Accountability Office (GAO) published a survey that revealed that 85 percent of the Air National Guard and Air Force Reserves personnel experienced adverse reactions following anthrax vaccination. This was significantly higher than the reported 30 percent claimed by the vaccine’s manufacturer. This survey also noted that between September 1998 and September 2000, about 16 percent of the pilots and aircrew members of the guard and reserve had (1) transferred to another unit (primarily to nonflying positions to avoid or delay receiving the anthrax shots), (2) moved to inactive status, or (3) left the military.    

This report also stated that Additionally, an estimated one in five (18 percent) of those still participating in or assigned to a unit in 2000 - that is those who had not already changed their status - indicated their willingness to leave in the near future. Both groups, those who had already left and those indicating their intention to leave, ranked AVIP [Anthrax Vaccine Immunization Program as a key factor in their decision to leave or change their participation.   

On October 27th, 2004, U.S. District Court Judge Emmet G. Sullivan ordered the Department of Defense (DOD) to immediately halt anthrax vaccinations after ruling that the mandatory vaccination program was illegal. Sullivan initially ruled in 2003 that the FDA had never approved the vaccine and ordered the vaccination programs to be stopped; however, eight days later, the FDA approved the vaccine based on an application made 18 years earlier, and the vaccination program was resumed. The Oct. 27, 2004 decision concluded that the FDA did not follow its own rules in declaring the vaccine safe and effective. Specifically, the individuals who filed suit regarding the mandatory anthrax vaccination argued that the FDA did not adequately review the vaccine’s effectiveness against inhalation anthrax. 

In January 2005, the FDA issued an "emergency use authorization" (EUA) that permitted the DOD to resume anthrax vaccination on a voluntary basis. In April 2005, Sullivan granted the DOD permission to continue vaccination programs based on the EUA guidelines. Military personnel would be provided with informed consent and permitted to decline vaccination without repercussions.  However, in October 2006, the DOD once again mandated anthrax vaccination for service members deploying to Korea, Iraq, and Afghanistan.  This mandate followed the December 2005 FDA ruling that reported the vaccine as effective against all forms of anthrax. 

Since 1998, BioPort, now Emergent BioSolutions, has delivered millions of anthrax vaccine doses, primarily to the U.S. Department of Defense as the sole source supplier of anthrax vaccine for the U.S. military. The U.S. government has also given the company millions of dollars in bailouts despite concerns that this money was not used appropriately and could not be accounted for. 

In 2009, the FDA granted Emergent Biosolutions a shelf life extension for its Biothrax anthrax vaccine, from three to four years.  In 2011, the U.S. government awarded Emergent Biosolutions a 5-year sole-source contract for the purchase of nearly 45 million doses of Biothrax. 

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.

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