Smallpox is a contagious viral illness caused by the variola virus. The virus can spread from an infected person through the air when there is fairly prolonged (1-3 hours) direct contact. It can also spread via body fluids, either by direct contact with fluids from an infected person or by touching objects that have been contaminated by infected body fluids. The last documented case of smallpox disease occurred in 1977. However, smallpox is still considered a possible biological threat.
An infected person usually begins to experience symptoms 12 to 14 days after exposure. Smallpox disease results in a fever and viral-like symptoms, followed by a rash that progresses from papules to pustules. Eventually the pustules form scabs and the scabs fall off. People with smallpox can spread the virus to others beginning when their fever is 101°F until all their scabs fall off.
There is no proven cure for smallpox. Historically, death has occurred in about 30% of cases. Giving smallpox vaccine soon after exposure to the virus can help to reduce the effects of smallpox disease. Vaccine given within 3 days after exposure can help prevent death. Vaccine given within 7 days after exposure can result in a less severe (modified-type) smallpox illness.
There is only one smallpox vaccine available in the United States. It is a live, attenuated vaccine made from vaccinia virus. Vaccinia virus is closely related to variola virus, which is the virus that causes smallpox. Immunity against vaccinia virus also provides protection against variola virus. It is administered using a bifurcated needle that is jabbed into the surface of the skin.
To reduce the chance of spreading the vaccine virus to other body parts or other people, please follow these recommendations:
Women receiving a smallpox vaccination should wait until the scab has fallen off and the vaccination site has completely healed before trying to become pregnant after vaccination. Generally, this means vaccinated women should wait four weeks after their smallpox vaccination. Until that time, effective measures should be taken to prevent pregnancy, such as abstinence, birth control pills, injections, implants, or IUDs. Other methods of birth control, such as condoms, diaphragms, spermicide, and natural family planning are less effective than abstinence.
Vaccinated men may wish to wait a similar amount of time before fathering a child. Until the vaccination site has completely healed, they can be the source of spreading vaccinia to a close contact (such as a sex partner). Covering the vaccination site is very important for both men and women.