Antibiotics can prevent anthrax from developing in people who have been exposed but have not developed symptoms. Ciprofloxacin and doxycycline are two of the antibiotics that could be used to prevent anthrax.

Each of these antibiotics offers the same protection against anthrax. Anthrax spores typically take 1 to 6 days to be activated, but some spores can remain inside the body and take up to 60 days or more before they are activated. Activated spores release toxins—or poisons—that attack the body, causing the person to become sick. That’s why people who have been exposed to anthrax must take antibiotics for 60 days. This will protect them from any anthrax spores in their body when the spores are activated.


How long does it take for anthrax to activate and release toxins?

timeline graphic to illustrate that anthrax spores can activate up to 60 days after exposure

Figurative animation showing a prescription bottle of antibiotics and an anthrax spore. A warm glow spreads from the bottle to surround the infection and stop it from growing.

Antibiotics work in two main ways, by killing the anthrax or by stopping the anthrax from growing. When the anthrax can’t grow anymore, it dies.

To learn more, you can watch the full video about anthrax and antibiotics.


Anthrax Vaccine Adsorbed (AVA) protects against anthrax. It does not contain any anthrax bacteria and cannot give people anthrax. It is not typically available to the general public. The vaccine is approved by the Food and Drug Administration (FDA) for two different situations.

Routine Occupational Use (Before Possible Exposure)

Anthrax vaccine is approved for use in three groups of adults 18 to 65 years of age who may be at risk of coming in contact with anthrax because of their job. These at-risk adults will receive the vaccine before exposure:

  • Certain laboratory workers who work with anthrax
  • Some people who handle animals or animal products, such as some veterinarians
  • Some members of the United States military

To build up protection against anthrax, these groups should get 5 shots of anthrax vaccine over 18 months. To stay protected, they should get annual boosters. The shots are injected into a muscle (intramuscular).

People who should not get the anthrax vaccine for routine occupational use include:

  • Pregnant women.
  • Anyone who has had a serious allergic reaction to a previous dose of anthrax vaccine.
  • Anyone who has a severe allergy to any component of the anthrax vaccine. Anyone with severe allergies, including allergy to latex, should tell their doctor.

For anyone with a moderate or severe illness, their doctor might ask them to wait until they recover to get the vaccine. People with mild illness can usually be vaccinated.

Post-Event Emergency Use (After Possible Exposure)

In November 2015, FDA also approved the vaccine for use after exposure to anthrax for people 18 through 65 years of age. In certain situations, such as a bioterrorist attack involving anthrax, anthrax vaccine might be recommended to prevent the disease in people after they have been exposed to the anthrax germs.

If this were to happen, people who were exposed would get 3 shots of anthrax vaccine over 4 weeks plus a 60-day course of antibiotics.

During an emergency, the only people who should not get the anthrax vaccine after possible exposure are those who have had a serious allergic reaction to a previous dose of anthrax vaccine. These people would receive the 60-day course of antibiotics only.

For more about anthrax vaccine, visit CDC’s Anthrax Vaccination webpage

Prevention and Treatment Recommendations

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