HEALTH & SCIENCE

Smallpox vaccine: Balancing the benefits and the risks

Despite increased public demand, the potential for severe reactions must be weighed against the threat of the disease before beginning widespread inoculations.

By Susan J. Landers, AMNews staff. Nov. 12, 2001. Additional information

Washington -- In recent weeks, the world has become a different place -- one in which fears of smallpox have re-emerged for the first time in decades.

Parents are calling pediatricians asking if their children could be vaccinated against the feared disease. But, of course, they can't be. There are reported to be only about 15 million doses of the vaccine in the nation -- vaccine that was basically left over from 1972, when the country's mass vaccination program ended.

In addition, physicians are cautioning those eager to receive the vaccine for themselves or their family members that the live-virus preparation of infectious vaccinia virus that is used to inoculate people against smallpox carries its own risks.

"This is not an innocuous vaccine," said Donald Henderson, MD, director of the Center for Civilian Biodefense Studies at John Hopkins University in Baltimore. He was recently named head of a federal advisory committee to assist the government in deciding when and if to begin another widespread smallpox vaccination program. Dr. Henderson is also known for his work in helping to rid the world of smallpox years ago.

"Before a recommendation could come forward to use smallpox vaccine, I think there would have to be a demonstrated risk," said Timothy Flaherty, MD, chair of the AMA Board of Trustees. "And right now, without having had a case of smallpox in the world since the early 1980s, there is no reason to use smallpox vaccine."

Side effects and adverse reactions from the smallpox vaccine range from fever to tissue necrosis and extensive lesions to encephalitis. A death rate of one per 1 million vaccinations is noted by the Centers for Disease Control and Prevention.

However, the threat that terrorists could spread the disease to a largely unprotected population has led the federal government to press for stepped-up production of the vaccinia vaccine.

Acambis PLC, a British company with facilities in Cambridge, England, has already signed a contract to produce about 50 million doses of the vaccine, and many of the nation's largest vaccine manufacturers are bidding on a federal contract to produce more.

The heads of the major pharmaceutical companies recently outlined a range of initiatives intended to help protect the public health. Among the initiatives are offers of free antibiotics to treat those exposed to anthrax and offers to develop and manufacture a smallpox vaccine.

Health and Human Services Secretary Tommy Thompson recently pledged that there will be enough vaccine for all Americans if the need arises. Key to physicians and others familiar with the dangers posed by the vaccinia vaccine are the words "if the need arises."

"I would never recommend it for mass inoculations at the present time," said Robert Edelman, MD, associate director for clinical research at the Center for Vaccine Development at the University of Maryland School of Medicine in Baltimore.

Dr. Edelman is leading one of four newly funded studies to measure the effectiveness of the existing stock of smallpox vaccine and to determine whether the current supply can be diluted in order to make more doses.

"In a mass vaccination, you're going to have several hundreds of deaths from the vaccine alone," he said. "About one in a thousand people will have some kind of reaction to the vaccine and I'm not talking about fevers and chills, they come with the territory," said Dr. Edelman.

The vaccine for smallpox was long known to carry danger, but the risk of getting the highly contagious disease, which carries a fatality rate of 30% or more, posed an even greater danger several decades ago.

Today, members of the public may be aware of the dangers posed by the vaccine, speculated Dr. Edelman. "But even though the risk of getting smallpox due to a bioterrorist event is small at the moment, people are so frightened and anxious that they are willing to take risks. It's a mind-set like everything in life."

VIG availability

With the potential for severe reactions so great, Michael J. Scotti, MD, AMA senior vice president for professional standards and a retired Army Medical Corps general, cautioned that vaccinia immune globulin -- used to treat complications of the vaccinia vaccination -- needs to be available and a distribution system in place.

However, VIG can only be derived from those recently vaccinated for smallpox. Except for a small number of smallpox researchers, no one has been vaccinated recently, noted Dr. Scotti. "If you are going to inoculate a million people, you might not have enough VIG."

Another item that may be in short supply is the bifurcated needle used to administer the vaccine. Instead of a simple injection, the procedure involves rapidly making 15 scratches, each about five mm long, using a forked needle that holds the proper amount of vaccine. The process draws blood and provides the vaccine with a route into the body.

If the vaccine "takes," a pox will develop after about seven to 10 days that eventually dries up and forms the traditional scar that can be seen over the deltoid muscles of those people who have been successfully vaccinated.

But even those who were inoculated as children may no longer be fully protected.

Since the vaccine is thought to lose effectiveness after 10 years, a revaccination would be necessary.

While vaccine production no longer involves live calves, thus ensuring a cleaner process, many physicians would like to see a newer, safer version of the vaccine developed so that if or when the decision is made to prophylactically vaccinate the whole U.S. population, there will be no issue of balancing the risk of the vaccine against the benefit of protection from the disease.

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Bioterrorism response from the CDC (http://www.bt.cdc.gov/)

Article, "Smallpox as a biological weapon," JAMA, June 9, 1999 (vol. 281, issue 22) (http://jama.ama-assn.org/issues/v281n22/ffull/jst90000.html)

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Additional information

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Ongoing coverage: Terrorism in America