United Press International - December 19, 2002
Steve Mitchell, UPI Medical Correspondent, in Washington)

In one of the most comprehensive analyses of a smallpox attack, a mathematical model of six different smallpox scenarios by the RAND Corporation found vaccinating the general public before an attack would only reduce the number of deaths if there were a release of the deadly virus in multiple airports.

In other scenarios involving infection of a laboratory worker, suicide attackers infecting themselves and spreading the virus on buses or subways, or terrorists spraying the virus into a ventilation system of a building, pre-vaccination did not reduce the number of deaths.

"As long as the risk of a smallpox attack is low but not zero it's not prudent to vaccinate the general public but it is prudent to vaccinate healthcare workers," Samuel A. Bozzette, the study's lead author and an infectious disease specialist affiliated with the Veteran's Administration's San Diego Healthcare System and RAND, told United Press International.

Administration officials have said information gathered by intelligence agencies does not indicate that an attack is imminent.

"There's no real reason to offer (the vaccine) to the public," Bozzette said. "Vaccinating individual citizens will not help the nation," he said. The president's decision not to vaccinate his family "should be an example for the nation," he said, noting that officials within the Bush administration were briefed on the RAND analysis prior to announcing the smallpox plan.

Bozzette noted both he and his wife will be vaccinated because they work with infectious diseases and are likely to be involved in a response to a smallpox attack. However, he added, "there's no way our parents, children or other relatives will be vaccinated because they know they are not helping the nation because the virus is slow moving and there would be time to put control measures in place."

In addition, there is a real risk because "smallpox vaccination is an intentional infection of the skin with a live virus that will make some people seriously ill or even kill them," he said.

The RAND analysis, which will appear in the Jan. 30 issue of the New England Journal of Medicine, presumed only about 60 percent of the U.S. population would elect to be pre-vaccinated, resulting in about 500 deaths. Assuming there was no pre-vaccination, the model concluded there would be seven deaths in the laboratory incident, 19 in the bus or subway attack, 300 in the release into the ventilation system, and up to 54,728 in the airport attack.

Although pre-vaccinating the general public only lowered deaths in the airport scenario, vaccinating healthcare workers lowered deaths in both the building and airport attacks.

If nearly all 10 million health care workers and emergency personnel in the United States were vaccinated, about 25 people would die. But this risk is justified because healthcare workers are particularly vulnerable to infection because they will be in close contact with smallpox victims if an attack occurs, Bozzette said.

However, Thomas Mack, a physician at the University of Southern California's School of Medicine, said in an accompanying article neither the general population nor healthcare workers should be vaccinated unless "evidence suggests that a massive attack or sustained biologic warfare is probable." This is because "the cost in deaths from vaccine complications will outweigh any benefit," said Mack, who investigated the way smallpox spreads in an outbreak three decades in Pakistan when he worked for the Centers for Disease Control and Prevention.

In an interview with UPI, Mack faulted the RAND conclusions because they are based on a model and it is very difficult to capture all the idiosyncrasies and human behavior involved in spreading the disease in a model. "Past experience is better for predicting," he said, noting previous outbreaks in Pakistan and Europe have shown the disease is not transmitted well in public settings and that most cases of transmission occur in hospitals among people who have close contact with the victim.

"I don't think smallpox is a disease that's going to spread like wildfire because we will be able to get it under control very fast," Mack said.

He compared smallpox to a minor threat such as a hand grenade rather than a major threat such as a large bomb. An attack "is likely to result in substantially fewer than 20 cases and 10 deaths," Mack writes in his article, noting this is a relatively small number compared with the hundreds of deaths that could result from widespread vaccination.

Kent Sepkowitz of the Infectious Disease Service at Memorial Sloan-Kettering Cancer Center in New York, points out another consideration for vaccinating healthcare workers is the contagiousness of the vaccine virus -- which is different from the smallpox virus and cannot cause smallpox.

The virus, which is called vaccinia, can cause complications including death, particularly in the high-risk groups, including people infected with HIV, cancer patients undergoing chemotherapy, organ transplant recipients on immunosuppressant drugs and people with skin conditions, such as eczema.

This is particularly worrisome because hospital workers probably will be in close contact with these patients and previous studies have shown recent vacinees can transmit the vaccinia virus to patients in the hospital setting, where it is fatal in as many as 11 percent of cases, Sepkowitz writes.

Several hospitals have announced they will not offer the smallpox vaccine to their employees due to concerns about the spread of the vaccinia virus to patients as well as complications that could occur in the healthcare workers themselves.

Bozzette conceded all the risks to healthcare workers cited above need to be taken into consideration. "However," he added, "our data ... indicates that at the prevailing levels of risk (of an attack), the nation as a whole would be better off if healthcare workers were vaccinated."

Instead of vaccinating millions of healthcare workers as Bush's program calls for, Mack suggests vaccinating a crew of about 15,000 medical and law enforcement personnel who are prepared to respond wherever they are needed in the event of an attack. These individuals also should be carefully screened prior to vaccination to weed out those infected with HIV or those with eczema to avoid complications of the vaccine, he said.

In addition, Mack calls for not admitting or treating suspicious patients at general hospitals because this is where the virus is likely to spread. Arrangements should be made to instead treat these patients at alternative facilities, such as commandeered hospices or nursing homes or even setting up Army field hospitals, if necessary, he said.

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