Smallpox Vaccine A Prickly Issue

By Robert Preidt

HealthScoutNews Reporter

Fear of a smallpox attack by bioterrorists against the United States has made some people eager for vaccination against the potentially deadly disease.

However, the health risks posed by such a vaccine suggest that one-quarter of all Americans shouldn't receive it, a new study says.

The reason: They may be at high risk for side effects that could cause serious illness or death, or might come in contact with people vulnerable to the vaccine, according to research from the University of Michigan Health System.

"Unlike other vaccines, smallpox vaccination carries with it a serious risk of adverse outcomes," says lead author Dr. Alex R. Kemper, an assistant professor in the department of pediatrics and communicable diseases.

Kemper and his fellow researchers used computer modeling to study the effectiveness and potential downsides of different kinds of smallpox vaccination campaigns. The new study is the first of the results to be made public.It appears in the April issue of Effective Clinical Practice.

The research recommends that any decision to resume large-scale smallpox vaccinations needs to take into account a number of factors. They include the likelihood of a smallpox attack, the effectiveness of other smallpox-control measures, and the potential harm of the smallpox vaccine.

Kemper's team examined data from prior smallpox vaccination campaigns in the United States, mostly from 1968. It concluded that a national immunization campaign for people between the ages of 1 and 29 would include 82.5 million people.

Of those, 190 people could be expected to die from vaccine complications. Another 1,600 would suffer serious but survivable side effects, such as encephalitis, and 15 million people would have less serious side effects such as fever and rash.

A larger campaign that targeted people from 1 to 65 years old would vaccinate 178.5 million people. Among that group, there would be 285 deaths from vaccine complications, another 4,600 people would suffer the serious side effects, and 32 million people would have minor side effects.

Those most at risk of complications from the smallpox vaccine include children less than 1 year old, and people with compromised immune systems. They include people with HIV /AIDS, those undergoing chemotherapy for cancer, and anyone receiving anti-rejection drugs after an organ transplant.

People with eczema are also at risk from the smallpox vaccine, Kemper says.

Vulnerable people could suffer health consequences even if they weren't vaccinated. That's because someone recently vaccinated can pass the vaccine virus to others, Kemper says.

Smallpox kills about 30 percent of the people it infects. There is no cure. Initial symptoms appear within seven to 17 days of exposure to the virus; they include high fever and head and back aches. A rash follows within two to three days, followed by pus-filled lesions.

The disease is spread mostly by infected saliva droplets when people come within a few feet of one another. It can also be spread in contaminated clothing or bed linen.

Smallpox was eradicated worldwide by 1980, and routine vaccination in the United States ceased in 1972.

Kemper says public debate is needed on the issue of a national smallpox vaccination campaign. It's a discussion that's become more relevant with the recent federal government disclosure that it could provide enough smallpox vaccine for everyone in the United States, he says.

"One of the reasons we did the study was to inform the debate, to try to put numbers on what the actual risk is," Kemper says.

The current federal plan to contain a smallpox attack is a "targeted" approach that would quarantine anyone exposed to the virus and vaccinate all people they came in contact with.

Kemper acknowledges there are a number of variables that make it difficult to accurately predict the effects of a national smallpox vaccination campaign.

The new vaccine is more pure than it was 30 years ago, and that would decrease some of the minor side effects, such as rash and fever. And there's better treatment available for people who do become ill as a result of vaccination.

One immunization expert agrees it's difficult to calculate the effects of a national smallpox vaccination effort using old data.

"I'm not in any way knocking their work. I'm saying it would be a challenge for anybody to come up with precise estimates of what the downside risks may be to having universal immunization," says Dr. John F. Modlin, a professor of pediatrics and medicine at Dartmouth Medical School.

But this study does contribute to public awareness and the debate about how to protect against a smallpox attack, says Modlin, who wrote an editorial accompanying the Michigan study.

"What's important at this stage is that the public be aware that this is an issue before the federal government, and there are going to be important decisions about how supplies of smallpox vaccine will be used," he says.

"We need to make a decision as to whether or not and how we want to employ it. That's going to be the focus of a pretty widespread discussion in the next few months. This article by Kemper and his colleagues is a nice start to raising awareness of the issue," Modlin says.

What To Do:

Find out more about smallpox from the Centers for Disease Control and Prevention or the World Health Organization.

This article posted May 25, 2002.

Smallpox Vaccine A Prickly Issue

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