July 7, 2003 ST. LOUIS - Adults who were vaccinated against smallpox as children can be successfully revaccinated by using diluted doses of the vaccine and with fewer side effects, according to research published by Saint Louis University this week in the Journal of the American Medical Association.
"We saw fewer adverse reactions in the participants who had been vaccinated before," said Sharon Frey, M.D., the lead author of the study and an associate professor at Saint Louis University School of Medicine. "Our study included healthy adult volunteers between the ages of 32 and 60 who previously had been vaccinated. Our comparison group consisted of individuals who were otherwise healthy and between the ages of 18 and 31, who had never received a smallpox vaccination."
In addition to Dr. Frey, co-authors of the article are Frances K. Newman and Robert Belshe, M.D., both from Saint Louis University, and Lihan Yan from the EMMES Corp. in Rockville, Md. The full article can be accessed at the JAMA website: http://www.jama.com.
In previous studies by Frey and colleagues, published in the New England Journal of Medicine, researchers found that that the country's limited stockpile of the smallpox vaccine could be diluted up to 10 times and retain its potency in individuals who had never before been vaccinated. The results of these studies suggested the vaccine could be stretched to protect a greater number of Americans from the highly contagious virus, which public health officials fear terrorists might use in a biological attack.
"Our new study further suggests that it's possible to use the same vaccine dilution in people who have been vaccinated before and those who haven't," Frey said.
Frey said that routine smallpox vaccinations stopped during the early 1970s after the disease was certified as eradicated by the World Health Organization. "Many adults in the United States received the smallpox vaccine as children, so we conducted this study to see if these vaccinations given many years ago would confer any protection," Frey said.
Dryvax, the smallpox vaccine under study, is no longer produced, and there are limited supplies available in the United States. In the modern era this was the first research study to examine the immune response of the Dryvax vaccine in diluted doses in adults who were vaccinated as children.
Frey said this research sets the stage for a larger-trial. This phase one trial involved 90 participants, all at the Center for Vaccine Development at Saint Louis University.
Established in 1836, Saint Louis University School of Medicine has the distinction of awarding the first M.D. degree west of the Mississippi River. Saint Louis University School of Medicine is a pioneer in geriatric medicine, organ transplantation, chronic disease prevention, cardiovascular disease, neurosciences and vaccine research, among others. The School of Medicine trains physicians and biomedical scientists, conducts medical research, and provides health services on a local, national and international level.
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