Side effects of smallpox vaccine

FDA Consumer, May-June, 2004

The FDA has issued draft guidance on developing drugs to treat the side effects of vaccination against smallpox, a disease caused by the variola virus.

Routine vaccination for smallpox in the United States ended in the 1970s when the disease stopped occurring naturally. But because smallpox is a potential agent of terrorism, large-scale vaccination could be necessary in an emergency.

The smallpox vaccine is made from a virus called vaccinia, a "pox"-type virus related to smallpox. It contains the "live" vaccinia virus--not dead virus, like many other vaccines. When given before exposure to variola virus, the live vaccinia vaccine substantially protects most people against smallpox for at least several years. Also, if given within a few days after initial exposure, the vaccine may prevent or lessen the impact of smallpox infection.

But the vaccine can cause serious complications, such as severe infection at the site of vaccination or other areas of the skin. The vaccine can also cause the virus to spread to other parts of the body or to other people. Other side effects of the vaccine include rashes, inflammation of the brain and heart, and smallpox infection of a fetus.

Groups at increased risk for complications include people with suppressed immunity, pregnant women, people with a history of eczema and other chronic skin diseases, and possibly people who have heart disease.

The FDA's draft guidance is available online at www.fda.gov/cder/guidance/5518dft.pdf.>