What is the anthrax vaccine?
The human anthrax vaccine is an immune system stimulant that allows the body to form protective antibodies against anthrax bacteria. Anthrax Vaccine Adsorbed (AVA) is made from bacterial antigens as a cell-free filtrate. It does not contain live bacteria capable of producing disease. First licensed for general use in 1970, it is currently manufactured and distributed by BioPort, Corporation, Lansing, Michigan. This vaccine has been FDA-approved as a standard vaccination, which means it is has not been experimental or investigational since 1970. The vaccine also contains tiny amounts of aluminum hydroxide to help stimulate the immune system. Human anthrax vaccines are different than those for animals, which contain live, but weakened bacteria. The human and animal forms are not interchangeable.
Who should receive pre-exposure vaccination?
Since anthrax is rare and usually transmitted by infected animals, the vaccine for domestic exposure has been limited to people likely to contract anthrax from their occupations. The U.S. military also vaccinates its personnel who may be exposed to anthrax during foreign operations.
The Advisory Committee on Immunization Practices has recommended pre-exposure anthrax vaccination for the following groups:
- Persons from 18 to 65 years old who work directly with the organism in the laboratory
- Persons from 18 to 65 years old who work with imported animal hides or furs in areas where standards are insufficient to prevent exposure to anthrax spores.
- Persons from 18 to 65 years old who handle potentially infected animal products in high-incidence areas.
- Incidence is low in the United States, but veterinarians who travel to work in other countries where incidence is higher should consider being vaccinated.
- Military personnel deployed to areas with high risk for exposure to the organism (as when it is used as a biological warfare weapon).
People who have lost their spleen (asplenic) due to surgery, disease or trauma may safely take the anthrax vaccine. Since the vaccine contains no live bacteria and asplenic patients are more susceptible to serious infections, vaccination is especially important in this population if there is any chance of anthrax exposure.
Who should receive post-exposure vaccination?
The vaccine may be used in those exposed to anthrax, in conjunction with antibiotic therapy, to reduce the severity of the disease. Post-exposure vaccination alone will not reliably prevent disease. At least three doses should be given for post-exposure prophylaxis. AVA may be given with penicillin or doxycycline for naturally occurring anthrax, as well as with ciprofloxacin, ofloxacin or levofloxacin for resistant strains. Even though post-exposure AVA may reduce the incidence and severity of anthrax, antibiotic therapy is still required for at least 4 weeks due to prolonged survival of spores in the lungs. Ciprofloxacin remains the only FDA approved drug for large inhalation exposures of anthrax.
Who should not receive the AVA vaccine?
Some people are not candidates to receive AVA. The CDC does not currently recommend vaccination for high-risk groups such as paramedics, police and physicians at high risk of exposure when responding to bioterrorism events. This is because the risk of exposure and a comparison to the risks of the vaccine cannot be calculated.
Those who have had a serious allergic reaction to anthrax vaccine or any of its components should not be given future doses. Those who have recovered from a clinical anthrax infection should not be given the vaccine. People with a moderate to severe infectious illness should not begin an elective vaccination program until they have recovered.
What about pregnancy and breastfeeding?
During the past 30 years, there has been no evidence of harm to pregnant women or their fetuses. Anthrax vaccination is listed as Pregnancy Category C. Despite a lack of evidence showing harm, pregnant women should be vaccinated only if absolutely necessary. Breast feeding mothers may receive AVA without any fear of passing anthrax to their infants.
How is the anthrax vaccine given?
In order to assure complete immunity with adequate production of anti-anthrax antibodies, an initial regimen of six doses of vaccine is used. The immunization consists of three injections given 2 weeks apart followed by three additional injections given at 6, 12, and 18 months. Annual booster injections of the vaccine are recommended thereafter.
A number of studies on adults between the ages of 18 to 65 years have shown that the first three doses will provide a 95% response rate. This should provide general protection against inhalational as well as other forms of anthrax. A complete immunization schedule should provide protection for at least 12 months, with some protection to 24 months. If necessary, protective IgG antibodies can be measured to assure an adequate response has occurred.
What are the risks from the anthrax vaccine?
Any vaccine has some risk, but testing and safety standards assure that the risk of any vaccine is far less than the disease itself. The anthrax vaccine has been used extensively since 1970 with a good safety profile. Adverse reactions to AVA are tracked through the Vaccine Adverse Event Reporting System (VAERS).
Today, the safety of this vaccine is endorsed by a number of prominent organizations, including:
- Armed Forces Epidemiological Board
- Centers for Disease Control & Prevention
- Department of Defense
- Department of Health & Human Services
- Food & Drug Administration
- Various other respected public health organizations
- Working Group on Civilian Biodefense
- World Health Organization
Moderate systemic reactions to anthrax vaccination occur in less than two people out of every 1,000. Less than one person out of every 100,000 vaccinated will have a severe, life-threatening reaction. Mild local reactions with slight tenderness and redness at the injection site occur in about 30% of recipients. Severe local reactions are infrequent (less than one in 100) and consist of extensive swelling of the forearm in addition to the local reaction. Women appear to have vaccination reactions about twice as often as men. Certain neurologic and autoimmune disorders such as Guillain-Barre syndrome and systemic lupus erythematosus have occurred in those taking the AVA vaccine, but at no greater rate than the general population.
Long-term studies (10-20 years) of over 1,500 laboratory workers at Fort Detrick have not detected any adverse reactions from the anthrax vaccine. Studies of veterans deployed to the Gulf War have also not detected any symptoms or diseases associated with the AVA. This includes cancer, immune system disorders and fertility. These workers received an initial series and annual boosters, as well as other vaccines. The military continues to study vaccine recipients, but there is no need for any routine monitoring of individuals receiving anthrax vaccination.
What does a vaccination reaction look like?
Mild local reactions include stinging, redness and minor swelling at the injection site. This may occur within a short period of time and persist for a few days. More severe local reactions will result in an area of pain, redness and swelling extending beyond the area of the vaccination. Some local reactions may persist for several weeks.
Mild systemic vaccination reactions may include chills, mild fever, muscle aches, headaches, loss of appetite and nausea. These usually resolve with acetaminophen or ibuprofen in a day or two. More serious, allergic, reactions can cause high fever, itching, a diffuse red rash (hives), wheezing, difficulty breathing, chest pain, throat swelling and collapse.
Table of Vaccine Side Effects
|Mild, Local Reactions||Incidence (%)|
|Local redness, pain, itching||10-15|
|Moderate Local Reactions||Incidence (%)|
|Large swelling, redness||1-5|
|Mild Systemic Reactions||Incidence (%)|
|Chills or fever||5|
|Severe Systemic Reactions||Incidence (%)|
How are vaccination reactions treated?
Local reactions can be treated with warm compresses and acetaminophen or ibuprofen for pain. Very large areas of swelling may respond to cold compresses for a day or two, followed by heat. Mild itching or hives may be treated with 245-50 mg of diphenhydramine (Benadryl). Anyone with immediate reactions of large hives, facial swelling, difficulty swallowing or breathing or chest pain should receive immediate medical treatment.
Continue to Anthrax Outlook
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