Smallpox Defense Plan Stresses Containment
Government guidelines don't call for mass inoculations ahead of time
TUESDAY, Nov. 27 , 2001 (HealthDayNews) -- A government blueprint for dealing with a smallpox attack calls for a limited vaccination program to contain outbreaks rather than giving a shot to every American.
The document, from the Centers for Disease Control and Prevention, is a retooling of an infection control plan developed after smallpox was declared eradicated in 1980.
The guidelines don't call for mass vaccinations before an attack occurs, since the risks of serious adverse reactions, although low, are serious. Nor do they say people should be immunized against their will.
Instead, at the core of the strategy is the proven approach of "ring vaccination." Ring vaccination, or "search and containment," is a basic disease-hunting gambit of locating infected people, "and then identifying and locating those people who come in contact with that person and vaccinating those people in outward rings of contact," says Dr. Harold Margolis, the CDC's senior adviser for smallpox preparedness. "This really then produces a buffer of immune individuals and was shown to prevent smallpox and to ultimately eradicate this disease."
Margolis and other government infection experts spoke yesterday at a teleconference with reporters to announce the guidelines.
When smallpox was rampant, the virus killed 30 percent of people infected, and some rare forms of the disease had death rates approaching 100 percent, according to the CDC guidelines. The microbe has a incubation period that lasts 10 to 12 days. During that time patients aren't infectious, but they become so after developing a rash and severe malaise.
This period is of particular concern for disease officials, because anyone who comes within about six feet of an infectious patient is at risk of contracting the deadly virus. As a result, the CDC recommends quarantines and other methods of isolating patients to corral the disease.
Dr. Lisa Rotz, a CDC bioterror expert, says the vaccine could be made available anywhere in the country within "hours" of a case being detected.
The government is also trying to establish how safely its existing stock of roughly 15 million doses of smallpox vaccine can be thinned while providing ample protection against the infection.
In an ongoing study, 77 people have so far been inoculated with diluted vaccine, and each has developed the signature "take" showing an immune response to the shot, says Dr. D.A. Henderson, director of the Office of Public Health Preparedness at the Department of Health and Human Services.
"So it looks very encouraging not only for one-to-five [one dose covering five people], but with a little bit of perhaps a cushion for even one-to-10. But I think if a problem occurred today and we needed the vaccine, we'd be ready to go in one-to-five immediately," Henderson says.
Health and Human Services Secretary Tommy Thompson has asked Congress for money to stockpile 300 million doses of smallpox vaccine.
Officials are also working with scientists to make more vaccinia immunoglobulin (VIG), the only known treatment for serious adverse reactions to smallpox vaccine, which include severe eczema and a progressive and potentially deadly die-off of skin around the area of the injection. Rotz says that between her agency and the Department of Defense, the government has enough VIG to treat about 600 adverse reactions to smallpox vaccine.
A report last June from the CDC predicts an overall complication rate of 108 cases per 1 million people re-vaccinated against smallpox. The number is roughly 11 times higher for those getting the shot for the first time.
VIG isn't recommended for most complications. But if tens of millions of Americans required immunization in the event of a smallpox threat, the current supply would be inadequate to treat the likely reactions for which it is effective, says Dr. Carol Tacket, a University of Maryland smallpox expert.
Smallpox vaccination in the United States ended in 1972.
What To Do
For more on bioterrorism and what officials are trying to do to stop it, try the National Memorial Institute for the Prevention of Terrorism or the Centers for Disease Control and Prevention.
For a history of the smallpox vaccine, check out Stanford University.