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Real Risks of Smallpox Debated
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Dec. 19, 2002 — The real risks from smallpox are addressed in several reports released online early today, to be published in the Jan. 30, 2003, issue of the New England Journal of Medicine (NEJM). The messages of the reports can be summarized as:
Risk of Smallpox Bioterrorism A smallpox attack on an unvaccinated U.S. public would be "catastrophic," according to D. A. Henderson, MD, MPH, Johns Hopkins University distinguished service professor and senior science advisor to the secretary of the Department of Health and Human Services. Dr. Henderson's standing — he was a leading force in the global eradication of smallpox — convinces some bioterrorism experts that a smallpox attack is a worst-case scenario. Others are not so sure. One is Kent A. Sepkowitz, MD, director of infection control at Memorial Sloan Kettering Cancer Center and associate professor of medicine at Weill Medical College, Cornel University, New York. "Remember Y2K. This is a comparable nonevent," Dr. Sepkowitz told Medscape. Another is Thomas Mack, MD, MPH, professor of preventive medicine at Keck School of Medicine, University of Southern California, Los Angeles. Like Dr. Henderson, Dr. Mack is a veteran of the world war on smallpox. He led teams that investigated some 100 smallpox outbreaks. His NEJM Sounding Board article argues that smallpox is overrated as a bioterrorist weapon. "A smallpox attack is not a worst-case bioterror scenario," Dr. Mack told Medscape. "People greatly exaggerate the danger to the population not directly affected. They picture smallpox being transmitted like wildfire, and that doesn't actually happen. It is more like a grenade than like a dirty bomb. Once the initial wave of infections is over, mopping up is relatively simple." Unlike many other diseases, people with smallpox can't infect other people until they start to feel ill — a couple of weeks after infection. And if people know they've been exposed, getting vaccinated within a few days often can keep them from getting sick. Both these facts mean that health workers have time to stop a smallpox epidemic before it gets out of hand. "Suppose the worst case: the aerosolization of live smallpox virus applied to a substantial population, say into a shopping center," Dr. Mack said. "Maybe if there was some way to keep it in the air, then, yes, under very extreme circumstances you could infect a large number of people. But the average number of people they infect is not going to change [from what we've seen in natural epidemics]. They don't get smallpox from weaponized virus any more, but from somebody's mouth. If they are put in hospitals, they will be dangerous. But once a first case appears, every community will find a place to put people away from the general hospital population." Another NEJM article calculates the risks from various smallpox-attack scenarios. It considers a range of smallpox outbreaks ranging from an accidental laboratory release to a major bioterrorist attack on a large airport. The researchers found that even a worst-case scenario does not justify mass public vaccination before there is an attack. Samuel A. Bozzette, MD, PhD, is senior scientist for RAND Health Care and the Veterans Affairs San Diego Healthcare System. Dr. Bozzette and colleagues estimate that a large airport smallpox attack could kill more than 40,000 people if the public wasn't vaccinated. It would kill nearly 13,000 people if the public were vaccinated beforehand. All these deaths would happen only in a "what if" scenario; nobody really knows whether such smallpox weapons even exist. But vaccination against smallpox would result in nearly 500 very real deaths. "The main issues are that smallpox isn't an instant killer, and that there is a lot of vaccine on hand," Dr. Bozzette told Medscape. "If there is an attack, there will be time to carry out a widespread vaccination program." The study finds that advance vaccination of healthcare workers is worthwhile -- but mass public vaccination is not. So would Dr. Bozzette get the smallpox vaccine? What about his family? "I think we can look to the example of what the President is doing with his family as what an informed judgment might look like," Dr. Bozzette said. "I am an infectious-disease specialist; I am going to be vaccinated. My wife is a pathologist; she is going to be vaccinated. But my children, my parents, my sisters and their children are not going to be vaccinated. Our family knows they are not helping the nation by getting vaccinated. They understand that even if there is an outbreak they are not likely to be infected and that there will be time to get vaccinated."
Learning About Smallpox
One of the most striking of the NEJM articles is a survey of what Americans know — and, mostly, don't know — about smallpox and smallpox vaccination. Robert J. Blendon, ScD, professor of health policy and political analysis at the Harvard School of Public Health, and colleagues conducted telephone interviews with a national sample of 1,006 adults. Dr. Blendon said there is a serious lack of knowledge, which means most people aren't able to make informed choices about whether to get vaccinated.
"There hasn't been a smallpox case in the U.S. — or in the world — in recent years," Dr. Blendon told Medscape. "Many people think there's been a recent case and it makes them more nervous. And people have to understand that there is not an effective treatment — some 80% think there is — so they may not understand the importance of early vaccination. They are not aware of the biggest public health message. That is, if you think you are exposed and get vaccinated in two or three days, you won't get symptoms."
Smallpox Vaccine Risks
It is known that many people will suffer adverse effects from the smallpox vaccine, and some — an estimated one to five in a million — will die. If the entire U.S. population is vaccinated, about 150 people are likely to die. One adverse effect of mass vaccination could be the accidental spread of the live-virus vaccine from a vaccinated person to an unvaccinated person. Immunosupressed people — such as transplant recipients, people taking immunosuppressants for arthritis and other conditions, and cancer patients on chemotherapy — are at enormous risk of vaccine complications. But are these people at risk from vaccinated people? Not much, according to the NEJM report by Dr. Sepkowitz. The Weill Medical College professor took a careful look at all the medical literature on the topic. "The vaccine virus is very uncontagious," Dr. Sepkowitz told Medscape. "It would take the wrong person being in the wrong place at the wrong time — and a [break with] standard infection control practices in hospitals for a person to get secondary disease. The risk will be small but not zero." Dr. Mack, however, argues against mass public vaccination. "This is the most dangerous live vaccine we have," he says. "It is going to kill people. It may be just a few people in a million, but it still will kill people. Overall, vaccinating people in general is not cost-effective. It will hurt more people than it helps. I think even vaccinating people who work in hospitals is not effective. We will hurt more people than we save. If someone would show me evidence that someone is planning sustained multiple attacks, I would change my mind."
Questions About Mass Vaccination Smallpox vaccination likely will be available for all Americans by 2004, including nonemergency healthcare professionals. Deciding whether to get vaccinated involves weighing whether the benefit is worth the risk. "Decisions are best made on a rational, factual basis and not on the basis of fear," Edward W. Campion, MD, NEJM senior deputy editor, told Medscape. "Physicians do have a major role. If there is going to be any type of widespread vaccination, patients are going to be coming to doctors to ask, 'Should I be vaccinated or not, what is your opinion?' " This makes it more important than ever for physicians to be informed and to be aware that they are role models. "At this moment I am making the decision as [a] front-line person to get vaccinated, but I am not having my family vaccinated," Dr. Blendon said. "That is important for people to know. It is more important for patients to know what their doctor says than what a cabinet secretary says. Physicians are critical. People are going to be watching what they say."
Bioterrorism from a Christian Perspective
Ref:
N Engl J Med. Published online Dec. 19, 2002. Daniel J. DeNoon Anthony Reinglas Reviewed by Gary D. Vogin, MD
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