A Smallpox Shot in the Dark

Sixty percent of Americans would opt for smallpox immunization if the vaccine were available, according to a recent poll, and U.S. health officials have just negotiated the purchase of enough vaccine for everyone in the United States. Those two facts may be a prescription for bad medicine. Medically and epidemiologically, smallpox is the most feared and potentially devastating of all infectious agents. It spreads from person to person, primarily via droplets coughed up by infected persons, via direct contact, and from contaminated clothing and bed linens. Smallpox is fatal in approximately a third of previously unvaccinated persons who contract the disease. For weeks, the media have raised the specter of terrorists using smallpox virus as a weapon. The German government has bought six million doses of vaccine, and pressure is mounting in the United States for widespread, or even universal, vaccination. (Routine smallpox vaccinations ceased in this country in 1972.) The U.S. government has ordered 300 million doses of the vaccine, and at a recent hearing, U.S. Sen. Arlen Specter (R-Pa.) said it is just "common sense" to make it available to everyone who wants it. But is it really? The live vaccine consists of live vaccinia virus, which is closely related to smallpox virus. Impure and crude by the modern standards of recombinant DNA-derived, or gene-spliced, vaccines such as those that have been successfully deployed against hepatitis B since the 1980s, the smallpox vaccine is not very different from the one introduced by the English physician Edward Jenner in the 18th century. It can provoke various serious side effects, including rashes; spreading from the inoculation site to face, eyelid, mouth or genitalia; and generalized infection. Approximately one in every 300,000 vaccinations causes encephalitis, which can lead to permanent neurological damage; and between one and three in every million die. Thus, vaccinating the entire population would be expected to kill as many as a thousand Americans, and maim and disfigure many others. Moreover, that assumes that the newer, ostensibly incrementally improved versions of the vaccinia vaccine are no less safe: Federal regulators have been uncharacteristically lax about requiring evidence of safety and efficacy in a drug intended for healthy individuals. If the re-emergence of smallpox were likely, vaccination would be appropriate. However, smallpox virus no longer occurs in nature but is limited to two known, legitimate repositories, one in the United States, the other in Russia (and perhaps to illegitimate ones in several other countries). It is, therefore, very difficult to obtain, and also to cultivate and disseminate. Also, smallpox is not immediately contagious after infection. It can be transmitted from one person to another only after a one- to two-week incubation period and the appearance of the characteristic rash, by which time the victim is prostrate, bedridden, and probably hospitalized. Therefore, the much-publicized scenario in which suicide terrorists infect themselves and then spread the disease widely through the population is not a realistic one. And although universal smallpox vaccination was phased out throughout the world during the 1970s, individuals who were vaccinated prior to that time retain significant immunity from these immunizations, both against contracting the disease and against a fatal outcome in case of infection. Scientists know a great deal about the long-term retention of immunity from a landmark study of 1163 smallpox cases in Liverpool in 1902-1903. Among those infected, 7% of the people 50 or older who had received the vaccine as children experienced severe disease and death, while 26% of unvaccinated people in that age group contracted serious cases of smallpox and all died. Even if an outbreak were to occur, public health authorities know how to respond. Control depends on early detection, quarantine of infected individuals, surveillance of contacts, and focused, aggressive vaccination of all possible contacts—an approach dubbed "quarantine-ring vaccination." Approximately 15 million doses of smallpox vaccine are available in the United States, and data suggest that these would still be effective if diluted fivefold, to yield 75 million. Moreover, the federal government has taken steps to cope with the possibility of a terrorist attack involving smallpox by educating doctors to recognize the disease and by vaccinating small teams of experts who can rush to any part of the country to confirm the diagnosis and contain and treat an outbreak. The city of New York has begun to map out various locations where residents would go to be immunized should mass vaccinations be necessary. In summary, given the difficulty of estimating the risks and benefits of vaccinating against a nonexistent disease using a vaccine that carries known, serious, sometimes-lethal side effects, one must agree with the conclusion of David Busch, head of infectious diseases at California Pacific Medical Center in San Francisco. "It's inappropriate" to vaccinate the entire country for a disease whose threat is only theoretical, and immunization should only be given "as needed, not as desired." If federal officials act otherwise, they will be more in the realm of public relations than public health. Even the expenditure of upwards of a billion dollars to stockpile 300 million doses of smallpox vaccine is arguably in the category of political cover. Far better, surely, to use those resources to ensure that susceptible Americans are immunized against common and life-threatening infectious diseases such as influenza, hepatitis, and pneumococcal pneumonia. (Flu alone kills 20,000 in an average year.) Sherlock Holmes admonished in A Scandal in Bohemia that "it is a capital mistake to theorize before one has data." It is worse to make the wrong decision after one has data. Henry I. Miller (miller@hoover.stanford.edu), MD, is a fellow at the Hoover Institution and the author of To America's Health: A Proposal to Reform the Food and Drug Administration (Hoover Institution Press).

A Smallpox Shot in the Dark

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