Merck Manual

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Smallpox Vaccine

By

Margot L. Savoy

, MD, MPH, Lewis Katz School of Medicine at Temple University

Last full review/revision Oct 2020| Content last modified Oct 2020
Click here for the Professional Version
NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version

In the United States, routine vaccination with the smallpox vaccine was stopped in 1972 because smallpox had been eliminated. Because the vaccine’s protective effects wear off after about 10 years, most people are now susceptible to smallpox.

Because samples of the virus have been stored, some people fear smallpox may be used by terrorists as a biological weapon. However, until an outbreak in the population occurs, smallpox vaccination is recommended only for people who have a high risk of exposure such as laboratory and health care personnel who work with the smallpox virus or related materials.

Enough smallpox vaccine has been prepared to vaccinate everyone in the United States if needed.

The smallpox vaccine contains live vaccinia virus, which is related to and provides immunity against the smallpox virus.

The vaccine is most effective when given before exposure. However, the vaccine may also be beneficial if given up to 4 days after exposure and can help prevent the disease or limit its severity.

For more information, see Centers for Disease Control and Prevention's (CDC) Smallpox: Prevention and Treatment statement.

Administration

To administer the smallpox vaccine, doctors rapidly jab a small area 15 times with a specially designed needle that has been dipped in the vaccine. Then the vaccine site is covered with a dressing to prevent the vaccina virus from spreading to other body sites or to other people.

Vaccination is considered successful if a small blister develops about 7 days later. If it does not appear, people are given another dose.

Vaccination is dangerous for some people, especially those with a weakened immune system (such as those who have AIDS or who take drugs that suppress the immune system), those with skin disorders (particularly eczema), those with eye inflammation, and those who are pregnant.

Side Effects

Fever, a general feeling of being ill (malaise), and muscle aches are common the week after vaccination.

Serious side effects occur in about 1 of every 10,000 previously unvaccinated people, and death occurs in 1 or 2 per million.

More Information

The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
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