By David Ruppe

Global Security Newswire

Containment—not mass vaccination—should be the U.S. strategy for dealing with the prospect of a terrorist attack using the deadly, rapidly spreading variola virus that causes smallpox, the Centers for Disease Control and Prevention said yesterday.

In an updated plan and guidelines for a national response to a smallpox attack (see GSN, Nov. 9), the federal health agency recommended using a “ring vaccination” strategy, which involves isolating, vaccinating, and closely monitoring people suspected of contracting the disease as well as those with whom they may have come in close contact.

Laboratory workers handling the virus, incident responders, law enforcement authorities, and health care providers working with diseased patients would also be vaccinated.

“Vaccinating and monitoring a ‘ring’ of people around each case and contact will help to protect those at the greatest risk for contracting the disease as well as form a buffer of immune individuals to prevent the spread of the disease,” the CDC wrote in an executive summary of the guidelines.

The recommendation comes as the United States is beginning to procure and stockpile enough smallpox vaccine to inoculate every man, woman and child in the country. That rush effort could be completed in six months.

Risks and Benefits

“The [containment] strategy would be more desirable than an indiscriminant mass vaccination campaign,” the CDC wrote, offering several reasons for that conclusion.

It said adverse side effects from the vaccine “would be expected to be higher” than the potential for casualties caused by an outbreak because the vaccinations might pose hazards to people with weakened immune systems, such as those with HIV or AIDS (see GSN, Nov. 21). Children under one year of age, adolescents and people with eczema, leukemia or lymphoma are also at risk.

“The risks vs. benefits of vaccination ratio would be higher in such a campaign because of the inevitable vaccination of people with high risk of adverse events and a low risk of smallpox,” the CDC wrote, although it noted there is not enough information showing risks to people with HIV.

Risks would vary from a prolonged fever in children to potentially fatal encephalitis. One death and hundreds of cases with serious side effects could occur for every million people vaccinated, according to the CDC and other researchers.

Some serious side effects could require treatment with a medicine called Vaccinna Immune Globulin (VIG), but there currently is not enough stored VIG to treat everyone that would experience serious side effects in a mass vaccination.

Additionally, large numbers of health care workers would be needed to administer a mass vaccination program and treat its related side effects, the agency said.

A Journal of the American Medical Association working group similarly concluded in 1999 that mass vaccination was not practical at that time in light of the limited quantities of vaccine and VIG in store. The group noted that if more vaccine was available, “preventive vaccination of some portion of the population will have to weigh the relative risk of vaccination complications against the threat of contracting smallpox.”  Click here to read the JAMA report.

Quarantine

According to the CDC plan, federal and state health officials jointly would be responsible for determining who would be included in a vaccination ring. Local law enforcement, fire and health-care personnel who do not come in direct contact with infected patients might also be vaccinated.

Smallpox is most commonly transmitted by internal contact with an infected person’s body fluids, usually from close, face-to-face contact, and less commonly through the air. Symptoms usually begin 12 to 14 days after exposure, starting with a two- to three-day high fever, malaise, and prostration with severe headache and backache, followed by a rash and lesions that may spread across the body.

Patients should be kept in specially ventilated rooms, health care workers would wear protective clothing that is specially laundered, and the patient’s condition should be closely monitored. Administering the vaccine in the first days after initial exposure to the virus can reduce symptoms and prevent the disease, according to the CDC.

However, the JAMA group was not optimistic about treatment. “At this time, the best that can be offered to the patient infected with smallpox is supportive therapy plus antibiotics as indicated for treatment of occasional secondary bacterial infections.

“No antiviral substances have yet proved effective for the treatment of smallpox, and the working group is not aware of any reports that suggest any antiviral product is therapeutic,” it said.

The overall mortality rate for smallpox is approximately 30 percent, according to the CDC.

The CDC plan calls for personnel dedicated to several activities, including surveillance, diagnosis and communication for potential outbreaks; education about the disease; rapid identification and vaccination of priority groups; surveillance, education, isolation and care of patients; investigation of outbreak source and risks to populations; and public communications.

Already Operational

The plan is already operational, according to the agency.

The CDC said much of its guidelines are derived from those used in the successful global effort that eliminated the disease in 1979. Smallpox, which has plagued mankind for thousands of years, was eradicated in 1979 through a massive worldwide vaccination and containment strategy.

There has been concern, however, that stores of the agent may secretly reside in laboratories abroad, and perhaps was obtained by terrorists, although the probability is considered low.

Routine vaccination was discontinued for the disease in the United States in the early 1970s and scientists believe protection from those vaccinations may have significantly diminished over time.

Production of the Dryvax vaccine, the only licensed in the United States, produced by Wyeth Laboratories of Marietta, Penn., was discontinued in 1980.

The Bush administration has requested $643 million for fiscal year 2002 to stretch the current stockpile of smallpox vaccine by diluting it and $509 million to speed up production of a total of 300 million additional doses, but some reports have suggested more money will be needed (see GSN, Nov. 7).

Click here for executive summary of CDC guidelines.

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