Getting a potentially deadly vaccine for a disease that has been totally eradicated would have sounded crazy to most Americans until recently. Forty years ago, routine smallpox vaccines killed 1 in every million Americans vaccinated: an acceptable risk, because smallpox killed millions worldwide. But after the disease was eradicated in the 1970s, health officials discontinued the vaccine, which is now considered too dangerous for general use. Today, with weapons-grade smallpox possibly in the hands of our enemies, citizens face important
questions: Has our definition of acceptable risk become too narrow? When it’s available, should we accept smallpox vaccination again?

Treatments for smallpox are in the works (see Best of What’s New: Medical Tech), but there is no cure, and the disease brings a 30 percent chance of death to anyone it infects. Yet many doctors fear vaccination more than an outbreak, because the potential for vaccine side effects–from fevers to encephalitis and death –may outweigh the odds of a smallpox attack.

A ferocious debate has erupted over who (if anyone) should receive the vaccine. All Americans born after 1971 (when vaccinations ceased) are vulnerable, and it’s likely those inoculated prior to ’71 are no longer immune. According to a recent poll, half of all Americans would choose vaccination if given the option. Federal officials favor offering vaccines to the public once 10 million health care workers are inoculated, and once the vaccine is licensed for general use, which isn’t expected until 2004. That’s when you may face a decision.

“Smallpox hasn’t gotten less deadly just because we haven’t seen it in 30 years,” says Dr. Matthew Davis, a physician and researcher at the University of Michigan. “If there’s a potential for a smallpox attack, which there seems to be, shouldn’t we protect ourselves?”

John Modlin, chair of the Centers for Disease Control Advisory Committee on Immunization Practices, disagrees: “If we were to immunize the entire population, even with screening, there would be a substantial number of adverse events, including death,” Modlin says.

The smallpox vaccine is made from a live virus called vaccinia–a relative of smallpox that causes a mild infection. Human immune systems generally fight it off easily, then develop immunity to vaccinia and the related smallpox. But some people’s immune systems can’t combat the virus, and vaccinia becomes a potentially deadly infection that spreads.

Death rates could be higher now than 30 years ago, Modlin says, because more patients have conditions, ranging from AIDS to asthma, that make them vulnerable. Michigan’s Davis disagrees, saying careful prescreening of the population would identify high-risk patients, who would not receive the vaccine. Having compared mathematical models of smallpox attacks in populations that did and did not receive inoculation, he likes the vaccine’s odds.

Although childhood immunizations were a cornerstone of smallpox eradication, the American Academy of Pediatrics opposes vaccinating children now, citing a lack of suitable testing. But Davis says his mind is made up. “My parents didn’t think twice about vaccinating me as a child,” he says. “Would I get the vaccine now if I could? Absolutely.”