October 11, 2002

VUMC begins second smallpox trial

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Diane Anders jokes as Dr. Kathryn Edwards administers the smallpox vaccine. (photo by Dana Johnson)

VUMC begins second smallpox trial

Vanderbilt University Medical Center researchers are launching a second trial of the nation’s existing supply of smallpox vaccine. This study will evaluate the frozen stockpile of Aventis Pasteur smallpox vaccine, and will measure the ability of the vaccine to stimulate immunity at three different dilutions. Another component of the study will access potential risk of those vaccinated to other “vaccine naïve” individuals.

The multi-center study, to be conducted by researchers at VUMC, the University of Iowa, and the University of Cincinnati, will address two questions: the appropriate dilution of the vaccine to stimulate immunity, and if those vaccinated pose any infectious risk to others with which they may come into contact.

VUMC’s previous smallpox vaccine study proved that both of the Centers for Disease Control and Prevention’s (CDC) stockpiles of Dryvax vaccine and the frozen Aventis Pasteur vaccine would produce an appropriate immune response at differing dilutions. Both lots of the vaccine, manufactured decades ago, have been in cold storage since the global eradication of the disease in the late 1970s.

“We proved in the first study that the frozen vaccine still works great, and could be diluted and remain effective,” said Dr. Kathryn M. Edwards, professor of Pediatrics in the division of Pediatric Infectious Diseases and the study’s principal investigator.

Edwards said of 60 participants immunized at VUMC in the previous trial there were 58 positive “takes” to the vaccine.

“The new study, with a larger number of participants, will focus just on the frozen Aventis Pasteur vaccine. The vaccine will be given at three strengths: full-strength, diluted 1-to-5, and diluted 1-to-10,” said Edwards.

Edwards and the VUMC Vaccine Trials staff are seeking 150 volunteers, ages 18-32, who have never had the smallpox vaccine. Criteria for exclusion from the study include a history of exfoliative skin disorders such as eczema or household contact with those with eczema, prolonged contact with children under 12 months of age, pregnancy, and people with autoimmune diseases.

“For this study we would like to target first responders such as police, fire and EMS workers as participants. Indications are that people in these professions will be strongly encouraged to receive the vaccine in the coming months,” Edwards said. “These participants may want to receive the vaccine ahead of their peers.”

It is understood that in the event of a biologic attack as many first responders as could be gathered would be necessary to perform mass vaccinations in a city like Nashville. In such an event, groups that may fall into the first responders category include infectious diseases practitioners, emergency medicine personnel, nurses, nursing students, and public health professionals.

According to the CDC’s “Smallpox Vaccination Clinic Guide,” a template for a mass vaccination campaign, a metropolitan area the size of Nashville would require 320 vaccinators to staff 20 vaccine clinic sites. The clinics would need to operate a minimum of 16 hours per day to vaccinate 1 million people in nine days.

Edwards also hopes for a more diverse representation of the population for this trial. “We would like to expand the groups of people participating so we will have a better understanding that the vaccine works equally well at a particular dilution in all races,” she said.

Another arm of this study, to be conducted at VUMC only, will examine how infective the vaccine may be. One current concern is whether a select group of people who have just received the vaccine may pose a health risk to others. The concern centers on whether vaccinia, the vaccine-based virus, may spread simply from an exposed vaccine lesion.

Edwards says many people are still worried about possible transmission of the vaccine to others. Since some first responders will be receiving the vaccine, researchers want to be sure there is minimal risk to others they may come in contact with.

“Participants will be followed closely and cultured throughout the study to make sure we have an understanding of whether vaccine poses a risk,” said Edwards. “We want to confirm what we’ve suspected all along — that this isn’t a risk to others.”

Dr. Thomas Talbot, a clinical fellow in Infectious Diseases who has an interest in the prevention of hospital-associated infections, will coordinate the infection surveillance sub-study, which will include laboratory testing of volunteers’ bandages and hands for possible contamination.

“We don’t think there is a risk to others created by those who are vaccinated,” said Talbot. “History teaches us this wasn’t a huge problem 30 years ago. Just as in the previous study, our participants will have their vaccine sites covered with occlusive dressings. This sub-study should quantify things and offer reassurance.”

Edwards says that with the number of participants enrolled at VUMC, along with an equal number of participants at the University of Iowa and the University of Cincinnati, the study should offer definitive answers as to the most effective dilution and overall safety of the 70 million to 90 million doses of frozen Aventis Pasteur vaccine.

Those interested in participating in the smallpox vaccine trial should call 343-8288 for more information.