CDC offers strategy to contain smallpox

Plans to protect the nation from a widespread outbreak are well received by public health officials.

By Susan J. Landers, amednews staff. Dec. 17, 2001.

Washington -- The federal government is taking a twofold approach to protect the nation from a smallpox outbreak.

On Nov. 26, the Centers for Disease Control and Prevention released a plan calling for carefully targeted smallpox inoculations that would maximize the ability of the 15 million doses of the vaccine now available to halt the spread of the contagious disease.

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However, the 15 million doses may be expandable. Early results from ongoing clinical trials indicate that each dose could be divided by five and retain its effectiveness.

Also, on Nov. 28, Health and Human Services Secretary Tommy Thompson awarded a $428 million contract to a small British biotechnology company to produce enough vaccine to inoculate everyone in the nation by the end of next year.

"Today, we find ourselves preparing for a difficult-to-imagine event, an intentional release of smallpox," said CDC Director Jeffrey P. Koplan, MD, MPH, when unveiling his agency's new response plan. "Although such a release might be unlikely, we must prepare for it so the spread of illness will be minimized."

The CDC's "Interim Smallpox Response Plan and Guidelines" is intended to provide a framework to guide local and state efforts toward developing their own workable plans.

The CDC estimates that 1 person will die of smallpox vaccine side effects for each million vaccinated.

The plan was generally well received by those on the front lines. "The fact that there even is a plan is a plus," said Georges C. Benjamin, MD, Maryland's Secretary of Health and Mental Hygiene.

Dr. Benjamin also stressed the interim nature of the plan. "We recognize that one of the first things we are going to have to change about the plan as the vaccine supply grows is who gets vaccinated."

Currently the CDC intends to vaccinate about 100 of its first responders. As supplies of the vaccine increase, Dr. Benjamin and other public health officials would like to vaccinate first responders in each state.

Containment ring

Another prime feature of the CDC plan is the "ring vaccination concept," in which suspected cases are isolated using contact tracing, close surveillance and vaccinations.

The vaccination and monitoring of a ring of people around each case is intended to protect those at greatest risk for contracting the disease and to form a buffer of immune people that prevents its spread.

The intention is to avoid an "indiscriminate mass vaccination campaign," according to the plan.

"Ring vaccination" would isolate cases via contact tracing.

The vaccine carries serious side effects and adverse reactions that range from fever to tissue necrosis, extensive lesions and encephalitis. About one in 1 million of those vaccinated will die as a result, according to the CDC.

In addition, the agency notes that there are insufficient supplies of vaccinia immune globulin, which is used to treat complications of the smallpox vaccine, to handle the many adverse reactions that would likely accompany a mass vaccination campaign.

Following identification of a case of the disease there should be time to carry out an effective targeted campaign of inoculations, noted health officials at a recent news briefing on the new plan.

They stressed that vaccine administered after an individual has been exposed to the virus still provides protection. "Around four days after exposure, there is still very good protection from vaccination," Harold S. Margolis, MD, CDC senior adviser for smallpox preparedness, explained.

In addition, it is unlikely that the disease could be widely spread if, for example, an infected person boards an airplane, said Donald A. Henderson, MD, MPH, director of the HHS Office of Public Health Preparedness.

"It's only when the rash begins that the individual transmits the disease," he said. After an individual is infected, there is an incubation period of 10 to 12 days when the individual feels well and is not able to transmit the infection.

After the incubation period the individual would have a fever for a couple of days and then the rash, he said.

"So, in fact, the people we're really concerned about are those who have a fever and then isolating them so they don't transmit the disease," said Dr. Henderson.