CDC's Response Plan for a Smallpox Emergency Excludes Mass Vaccination

WESTPORT, CT (Reuters Health) Nov 26 - The Centers for Disease Control and Prevention (CDC) on Monday released its "Interim Smallpox Response Plan and Guidelines." The plan does not call for mass vaccination in advance of a smallpox outbreak, because the risks associated with vaccination are deemed to outweigh the risks of exposure to the variola virus.

"Although smallpox was eradicated 21 years ago, we've had such a plan in draft for many years," Dr. Lisa Rotz, a CDC bioterrorism preparedness expert located in Atlanta, noted during a teleconference. The plan was developed in conjunction with state epidemiologists, bioterrorism coordinators, immunization program managers, and other health officials.

In recent years, the CDC and the public health service have expended considerable effort to expand connectivity nationwide for rapid communications, Dr. Rotz told Reuters Health. "With our HealthAlert network, we are in much better shape than we were several years ago to handle a bioterrorism attack," she said.

"We're releasing this interim plan so that state and local health departments can begin to think about state- and community-wide responses" in the event of an outbreak, Dr. Rotz added. For example, "planners can think about increasing their rapid response capability, identify personnel who would go immediately to help implement the guidelines, identify contacts of the cases and who would need vaccinations, as well as enhancing surveillance."

"At the heart of this plan is 'ring vaccination,' or search and containment," she continued. "The idea is to identify individuals infected with smallpox and identify those who have been in contact with the patient and vaccinate those in outward rings of contact. This strategy will produce a buffer of immune individuals."

The guidelines note that current supplies of smallpox vaccine are limited, but vaccine would be available "within hours" of a case being detected anywhere in the country, Dr. Rotz said.

Dr. D. A. Henderson, Director of the Office of Public Health Preparedness at the Department of Health and Human Services in Washington, DC, mentioned reassuring results from recent studies regarding methods to stretch supplies of the current vaccines.

"We've been getting some early reports from dilution studies, including from one site where they have vaccinated 77 individuals with diluted vaccine. Each person had a 'take,' so it looks encouraging for a one-to-five, perhaps even a one-to-ten dilution," he said.

Dr. Harold Margolis, CDC senior advisor for smallpox preparedness, pointed out that the vaccines have been used periodically over the years for laboratory workers. "The manufacturers have continued to conduct a battery of tests looking at potential microbial contamination and potency. All the vaccines have maintained their potency for over 20 years," he said.

Dr. Henderson wants to allay public fears regarding the potential consequences of a bioterrorism attack with the variola virus. "People are afraid that someone who is infected could spread the infection widely by traveling on an airplane."

That's not realistic, he pointed out, because there is an incubation period of 10 to 12 days, followed by 2 to 3 days of high fever and prostration with severe headache and backache. "It's only after that point, when the rash begins, that the individual can transmit the disease. However, people are likely to feel quite poorly and to be staying in bed, not traveling around the country."

In the guidelines, the CDC notes that the overall mortality rate associated with smallpox is approximately 30%. Two rare forms of the infection have a nearly 100% mortality rate, however: flat-type smallpox, which is characterized by severe toxemia and confluent lesions, and hemorrhagic-type smallpox.