Smallpox: Prevention

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Prevention

Vaccination

The smallpox vaccine (What is a PDF document?) is the only known way to prevent smallpox if a person is exposed. When given within 3 days of exposure, the vaccine can prevent or greatly reduce the severity of smallpox symptoms in most people. Getting a shot 4 to 7 days after exposure may also help. ³ The smallpox vaccine is made from the vaccinia virus, which is similar to variola virus, but safer. The vaccinia virus does not cause smallpox illness.

In the past, the smallpox vaccine was used to get rid of smallpox infection worldwide using:

• Ring vaccination of all people who were or may have been exposed to smallpox.
• Mass vaccination, to prevent infection of an entire population. Before 1972, all children in the United States were vaccinated before they started school. Routine smallpox vaccination ended in 1972 when smallpox risk in the United States became minimal.

Many disease-control experts think ring vaccination would be better than mass vaccination if there were a documented smallpox case today.

In the U.S., vaccination is being offered to medical personnel and other people who would be exposed to the virus if an outbreak of smallpox occurred (first responders). The smallpox vaccine does not give lifelong protection, and there are risks of a serious reaction from it. That's why routine smallpox immunization does not take place at this time. Health workers should always wash their hands or use a hand sanitizer after any contact with the vaccine or with the vaccination site.

The Centers for Disease Control and Prevention (CDC) has guidelines about who should not receive the vaccine. Those at increased risk of having complications from the vaccine include:

• Pregnant women, because of the risk of infecting the unborn baby.
• Breast-feeding women, because of the risk of infecting the baby.
• People with skin conditions, such as active or healed eczema.
• Babies younger than 1 year.
• People with an impaired immune system, such as those infected with human immunodeficiency virus (HIV) or cancer.
• People with serious, life-threatening allergies (anaphylaxis) to the antibiotics polymyxin B, streptomycin, tetracycline, or neomycin.

If you have heart problems or three or more risk factors for heart disease, you should not be vaccinated until more is known about a possible relationship between the smallpox vaccine and heart problems, including heart attack.

But if you are directly exposed to smallpox, you should be vaccinated even if you fall into one of these groups.⁵ In such a situation, the risk of death from smallpox is greater than the risk of having a harmful reaction to the vaccine.

Isolation and infection control

People who get this disease must stay away from others to help prevent it from spreading. Smallpox spreads by:

• Face-to-face contact with someone who has smallpox (usually someone who already has a smallpox rash).
• Direct contact with infected bodily fluids or an object such as bedding or clothing that has the virus on it.
• Exposure to smallpox virus released in the air (aerosol).

Ideally, an infected person would be isolated and cared for in a medical facility to prevent the spread of infection. Similarly, a person who may have been exposed should be vaccinated and isolated until it is certain he or she does not have the disease.

The CDC suggests that 3 types of facilities be set up where people can be monitored: one type for smallpox patients, one type for vaccinated people who have no rash, and one type for anyone exposed to the virus who has no symptoms and either hasn't been vaccinated or isn't sure if he or she was ever vaccinated.⁶

If you have been in contact with an infected person and you do not have symptoms—and you get the smallpox vaccine—you will be moved to the facility for vaccinated people.

If you have been in contact with a person who has smallpox and you decide not to get the vaccine, you may be kept apart from other people for 18 days. This means that you would not be able to be in contact with other people who have not been vaccinated. You would not be able to stay at home with others or go to work. You would be watched for signs of smallpox. And if symptoms appeared, you would be kept away from others to make sure you did not spread the infection.⁶

Clothing and bedding that have been in contact with an infected person should be washed in hot water with bleach. Hospital-strength disinfectants, such as hypochlorite and quaternary ammonia, can also kill the virus.

Scabs from smallpox lesions may contain the variola virus and could be infectious for months. They should be handled and disposed of as infectious medical waste.

Last updated:	January 31, 2007
Author:	Debby Golonka, MPH
Reviewed By:	William M. Green, MD - Emergency Medicine, Christine Hahn, MD - Epidemiology
Editors:	Susan Van Houten, RN, BSN, MBA, Pat Truman, MATC