Smallpox Vaccination Would Require Close Monitoring

By Merritt McKinney

NEW YORK (Reuters Health) - The widespread smallpox vaccination plan being considered by the US government may lead to many more cases of vaccine-related side effects than in the past, according to a panel of smallpox experts.

The smallpox vaccine contains vaccinia, a virus related to the smallpox virus that is used to trigger immunity to smallpox. The vaccine can cause severe side effects, including brain damage and even death, in a small percentage of people, particularly children and people with weakened immune systems. But even if individuals who are at high risk of side effects do not receive the vaccine, there are fears that they might be infected with vaccinia that is shed by others during the weeks after vaccination.

In a report in the October 16th issue of the Journal of the American Medical Association, the experts recommend that any smallpox vaccination campaign include careful screening and monitoring to minimize the odds that people at high risk of side effects will be exposed to the virus in the vaccine.

According to Dr. John M. Neff, of Children's Hospital and Regional Medical Center in Seattle, Washington, a "well controlled and very limited vaccination program" that includes thorough screening and education to exclude people at high risk of side effects and those in close contact with high-risk individuals may cause only a "very small" number of serious side effects.

But in comments to Reuters Health, Neff, who is the lead author of the report, said that "the same cannot be promised for a very extensive national campaign as now may be the direction of our current government."

To get an idea of the risks of smallpox vaccination for people who do not get vaccinated, Neff and his colleagues reviewed studies from the 1950s and 1960s, when children were routinely vaccinated against smallpox. According to these studies, unvaccinated people had a low risk of being infected with vaccinia as a result of contact with people who had been immunized against smallpox. For every 100,000 vaccinations, from 2 to 6 unvaccinated people developed so-called contact vaccinia. And in all of the studies, people who became infected with vaccinia usually contracted the virus through close contact at home, not in hospitals.

This may sound like reassuring news, but the population in 2002 is different from that of the 1960s in several important ways, according to the report. Since smallpox vaccination was stopped in the US in 1972, anyone younger than 30 does not have any immunity to vaccinia. If these people were to be vaccinated, they would be likely to shed vaccinia for several weeks.

Another concern, according to the report, is that the percentage of the population with a skin disorder that increases the risk of vaccine-related complications is much higher now than in the 1960s. Likewise, there are many more people with weak immune systems now, including organ-transplant recipients and people infected with HIV, the virus that causes AIDS.

Health care workers are another special concern, the authors suggest. There are more than 20,000 health care workers in the US who have HIV. And many health care workers have never been vaccinated against smallpox, meaning that after vaccination they would shed vaccinia that could infect patients with weakened immune systems.

Because of the risks of smallpox vaccination, "critical attention must be given to screening, counseling and monitoring," Neff's team concludes. A limited vaccine program that carefully tracks cases of contact vaccinia "could result in a limited number of cases of contact vaccinia." A large-scale program, however, could lead to more cases, according to the report.

An orderly, systematic approach along with careful screening to identify potential vaccinia-susceptible individuals and household contacts and close monitoring for adverse effects are essential to reduce the risk of transmission of vaccinia following smallpox vaccination," the report concludes.

"The real question," Neff said, "is why are we cascading into a seemingly unstoppable war scenario that causes us to react in an extreme fashion to a real or imagined fear of a bioterrorism event that otherwise would be highly unlikely.

"If we as health professionals cause serious injury or death as a result of our actions, then if these actions are ill-advised, we stand in danger of losing a very valuable public trust," Neff said.

The eradication of smallpox was officially declared in 1980, and according to the World Health Organization, national vaccination programs had stopped in all countries by the early 1980s. Officially, smallpox exists in only two laboratories--one in the US and the other in Russia. However, there are some concerns that other governments or terrorist groups may have samples of the deadly virus.

SOURCE: Journal of the American Medical Association 2002;288:1901-1904.

This article posted November 9, 2002.

Smallpox Vaccination Would Require Close Monitoring

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