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.”