The Smallpox Conundrum
That's the best way to protect ourselves against a bioterrorist attack?
Vaccinating before any release of smallpox virus offers certain protection for three to five years. After that, immunity wanes, but the vaccine still diminishes severe disease and death. Most states will start by vaccinating healthcare workers: Past studies have shown that half of the spread of smallpox occurs in hospital settings and that 1 in 5 who gets the disease is a healthcare worker.
There is also the question of who will get what vaccine. Dryvax, the older, dried vaccine that is currently available in the U.S. stockpile and was recently relicensed, is highly effective even when diluted. But it also has some fairly significant side effects, particularly for people at high risk of complications. Life-threatening reactions occur in about 52 people among 1 million vaccinated and include encephalitis, in about 12 per million vaccine recipients, and eczema vaccinatum, a reaction where the vaccinia virus spreads beyond the vaccination site. Eczema vaccinatum requires prompt and massive treatment with an antibody to vaccinia virus, made from the plasma of recently vaccinated donors. Right now there are only about 600 to 800 doses of this antibody in the United States. What's more, only some life-threatening reactions can be treated, which means that 1 or 2 people in a million will die from getting a smallpox vaccination. Less severe reactions--fever, rashes, sore arms, muscle aches--are common. Among young, healthy volunteers participating in a trial to determine the effectiveness of diluted Dryvax, 36 percent of those vaccinated felt sick enough to miss work or school.
Fear of sharing. Unless there is a massive outbreak, some others would also be advised to skip the inoculation: people with weakened immune systems, cancer, or AIDS, those who've received radiation treatments or organ transplants, pregnant women. Nor should their regular household contacts be vaccinated, because they could inadvertently spread the live virus from the vaccination site on their arm. Indeed, this inadvertent spread of virus is the most common complication of the smallpox vaccination. A semipermeable dressing covering the vaccination reduces the risk.
Last winter, the government ordered 209 million doses of a new smallpox vaccine from Acambis Inc. that is due to arrive soon. Testing and licensing the new vaccine should be completed by 2004. Many experts believe the Acambis vaccine will be safer than Dryvax, since it's grown in lab cultures rather than derived directly from the skin of calves.
Next comes the long-awaited campaign to educate citizens, and doctors, about the risks and benefits of voluntary vaccination. "During the anthrax experience, I saw a lot of people treated for anxiety with unnecessary antibiotics," says Susan Allan, director of health for Arlington County, Va. "I hope we won't see doctors treating patients for anxiety with a risky vaccine."
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