Online NewsHour: Smallpox Vaccine



	SMALLPOX VACCINE

The smallpox vaccine offers the only known method of protection from the disease, but it also carries its own risks. Find out more about how this vaccine works, what the potential side effects are and what plans exist for its future use.

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Dec. 4, 2001:
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Nov. 29, 2001: Preventing a smallpox outbreak

Nov. 20, 2001: Dr. D.A. Henderson, director of the new Office of Public Health Preparedness

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How the vaccine is different:
Most vaccines contain a dead virus, but protection from smallpox comes in the form of a live virus that is similar to smallpox. The presence of the live vaccinia virus in means that the vaccination site must be well cared for to insure that the virus does not spread to other parts of the body or to other people.
Protection the vaccine offers:
The vaccine has been shown to protect against smallpox for three to five years and is sometimes effective for more than 10 years. Researchers are working to determine what level of protection exists for those immunized as children.

Even if a person is exposed to the disease before they are vaccinated, the vaccine can help ward off the disease's effects. If it's administered within three days of exposure to smallpox, it completely or significantly modifies the disease in a majority of people. From four to seven days after exposure, the vaccine offers some protection or modifies the severity of smallpox.

The vaccine's risks:
While the vaccine is the best form of protection against smallpox, it does carry some risks. The live virus in the vaccine can cause rash, fever and head and body aches. Those most likely to suffer side effects are pregnant women; people with or who have had skin conditions, especially eczema; and people with weakened immune systems, such as transplant recipients, those who are HIV positive and patients receiving cancer treatments. In some cases, these side effects can be severe. Historically, out of 1 million people who received the vaccine, between 14 and 52 people had life-threatening side effects. Based on past experience, it is estimated that one or two people per million who are inoculated will die from adverse reactions to the vaccine.

The live virus that exists at the vaccination site can potentially spread to the vaccinee’s hands and then get passed along to those the vaccinee comes into contact. Thus, contact with some who recently received the vaccine could expose people with compromised immune systems to vaccine's potentially serious side effects. Getting the vaccine on one's hands can also be dangerous for the vaccinee since the virus could the spread to the eyes and possibly cause an eye infection that sometimes leads to blindness.

Plans for the future:
Routine vaccination of Americans against smallpox stopped in 1972 after the disease was eradicated in the United States.

Since Sept. 11, 2001, the U.S. government has updated its smallpox response plan and has ordered production of enough smallpox vaccine to immunize Americans in the event of an outbreak. On Oct. 16, 2002, the Advisory Committee on Immunization Practices, which advises the Centers for Disease Control and Prevention, endorsed a plan to immunize 500,000 health care workers in advance of an attack. The Bush administration is now putting the final touches on that plan.

Source: CDC

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