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Release: June 20, 2002

UI one of four institutions to take part in NIH smallpox vaccine study

The University of Iowa is one of four institutions nationwide selected to participate in a smallpox vaccine study aimed at increasing current stocks of the smallpox vaccine. The study is sponsored by the National Institute of Allergy and Infectious Diseases, one of the institutes within the National Institutes of Health (NIH).

The UI portion of the investigation will take place at the UI General Clinical Research Center and will be led by Jack Stapleton, M.D., professor in the infectious diseases division of the UI Department of Internal Medicine and director of the Helen C. Levitt Center for Viral Pathogenesis.

A total of 95 participants ages 18 to 32 years will be invited to take part in the trial. Most people in the United Sates in that age group have never been vaccinated against smallpox because common use of the vaccine ended in 1971, Stapleton said.

As a result, these individuals would be susceptible in the event of a biological attack that used smallpox. Current smallpox vaccine stores are not sufficient to provide inoculations to the entire U.S. population in the event that this becomes recommended.

"The science of this study is to determine whether a smallpox vaccine that has been stored for approximately 40 years still is effective and whether it can effectively be used at a lower dose than originally planned. If a lower dose is effective, the current vaccine preparation would be capable of vaccinating more people," Stapleton said.

Earlier this year, the Centers for Disease Control and Prevention (CDC) took its smallpox vaccine stock, known as Dryvax, which had been in storage for decades and tested it in full-strength and diluted forms. The CDC determined that the vaccine still worked in its original form and also was effective in vaccinating people when diluted by the ratio of 1:10.

The UI study will help determine whether the Dryvax vaccine can effectively inoculate people when diluted to a ratio even greater than 1:10 and whether the Aventis smallpox vaccine stocks are also effective in full-strength usage and at dilutions of 1:5 and 1:10.

"We will extend the study of Dryvax to see if additional dilutions are possible," Stapleton said. "We also will see if the Aventis vaccine has retained its potency at full dose and if it can be diluted like the Dryvax and still be effective. At least in the test tube, the Aventis vaccine appears to have retained its potency.

"There is a large stockpile of the Aventis vaccine in storage, and if it can be diluted 1 to 10, there should be enough vaccine available to vaccinate the entire U.S. population," he added.

A smallpox vaccine can reduce or prevent illness if given to a person within four days after they have been exposed to the disease, according to the CDC. Smallpox is spread among people by saliva and causes high fever, fatigue, headaches and backaches, and a rash that can eventually lead to scarring. Although the majority of people recover from the disease, nearly 30 percent of infected individuals die.

Stapleton said the vaccine can have side effects that include soreness in the arm, and approximately 10 to 15 percent of individuals who receive the vaccine may feel ill enough to miss work for a day or two. The vaccine is not smallpox, but a related virus called "vaccinia." Infection with vaccinia results in a mild infection that gives a person protection against smallpox.

After the last natural case of smallpox was documented in 1977, the World Health Organization declared the disease eradicated in 1980 and urged that people no longer be inoculated against it. People vaccinated for smallpox before 1972, when routine vaccinations stopped, may no longer have immunity against the disease. The U.S. military continued to routinely provide the smallpox vaccine to its troops until a few years ago.

At the federal level, experts are discussing smallpox vaccination policies that range from providing vaccinations after a biological attack or providing them to people proactively, including as a requirement for health care workers.

"There is consideration of whether or not we should immunize everyone now," said Stapleton, who also is a researcher and staff physician at the Veterans Affairs Medical Center in Iowa City. "These are important policy decisions that are currently under review."

For more information about National Institute of Allergy and Infectious Diseases smallpox research, visit the institute at For additional smallpox information, visit the CDC at or the NIH at

Smallpox-related images, some of which are in the public domain, are available by clicking on "Smallpox images" at the CDC site

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