Anthrax

Though in the 1950s an estimated 20,000 to 100,000 cases of anthrax occurred in the world each year, by the 1990s only around 2,000 cases occurred annually.

What is anthrax?

Anthrax is a spore-forming bacterium found in the soil throughout the world. The spores are so resistant to environmental conditions that they may survive in soil for 25 years-or possibly as long as a century. The spores cause a common disease among grazing animals, such as cows and sheep, and humans are usually infected via animal products, so vaccination of these animals in the U.S. is the rule. Infection manifests in three different disease forms, depending on which part of the body was primarily infected: the skin, the digestive system, or the lungs. The lethality of the disease also depends on its primary location: fewer than 5 percent of patients die from anthrax of the skin, 25 to 75 percent die from the digestive tract variety, and almost 100 percent die if the anthrax spores are inhaled into the lungs.

Antibiotics can be used after exposure to anthrax, but they must be used prior to the onset of symptoms, and treatment should include vaccination. Almost all cases of inhalational anthrax have resulted in death, even with post-exposure treatment.

What is the anthrax vaccine?

In 1970, an anthrax vaccine became fully licensed for use in humans. It does not contain live cells, unlike the vaccine used in animals. The vaccine is not licensed for use in children or pregnant women.

After the first dose of anthrax vaccine, additional doses are given 2 and 4 weeks later, and again 6, 12, and 18 months after the first. Boosters are given each year thereafter if exposure (or the risk of exposure) continues.

The vaccine is almost 93 percent effective at preventing the occurrence of skin anthrax in adults. No data on its effectiveness in children are available. Although there are too few cases of lung anthrax to test the vaccine's effectiveness against this form, which is most lethal, some studies with experimental monkeys indicate effectiveness. Because the duration of protection has not been established, boosters are recommended if exposure or risk is continued.

Who should and should not get the vaccine?

People who are at significant, continuing risk of acquiring anthrax should receive the vaccine. This includes some military personnel, as well as individuals with industrial, agricultural, or laboratory exposure to anthrax.

This vaccine, which has been required for some military personnel, has become quite controversial. Top military officials have said the vaccine is absolutely necessary to protect service personnel against hostile nations that have the capability of using deadly biologic agents in such places as the Persian Gulf region. Nevertheless, many military personnel concerned about adverse side effects have refused to receive the vaccine.

Anthrax vaccine should not be given to anyone with a hypersensitivity reaction to the vaccine. People who actually had anthrax in the past should not be vaccinated because they may develop severe symptoms at the site of injection.

What are the vaccine risks and side effects?

Reactions such as redness and tenderness within a day and lasting a day or two are not much more frequent than they are after the injection of sterile saltwater. Very rarely, swelling extends from the shoulder to the forearm. Also rare is the development of a painless nodule that lasts for up to three weeks at the site of injection. About 7 per 1,000 vaccine recipients get a slight headache or muscle aches, or simply do not feel well for a day or two. An estimated 5 out of 100,000 vaccine recipients will have a more significant reaction. For example, from 1990 to 1999 two cases of Guillain-Barré syndrome were reported to the Vaccine Adverse Event Reporting System after anthrax vaccine. But researchers do not know if the GBS was caused by the vaccine.