BACKGROUND The increased possibility of bioterrorism has led to reinitiation of smallpox vaccination. In Korea, more than 30 years have passed since the last smallpox vaccinations, and even people who were previously vaccinated are not regarded as adequately protected against smallpox. We evaluated the efficacy and safety of CJ-50300, a newly developed cell culture-derived smallpox vaccine, in healthy adults previously vaccinated against smallpox.

METHODS We conducted an open label, single arm, phase III clinical trial to evaluate the efficacy and safety of CJ-50300. Healthy volunteers, previously vaccinated against smallpox, born between 1950 and 1978 were enrolled. CJ-50300 was administered with a bifurcated needle over the deltoid muscle according to the recommended method. The rate of the cutaneous take reaction, humoral immunogenicity, and safety of the vaccine was assessed.

RESULTS Of 145 individuals enrolled for vaccination, 139 completed the study. The overall rates of cutaneous take reactions and humoral immunogenicity were 95.0% (132/139) and 88.5% (123/139), respectively. Although 95.9% (139/145) reported adverse events related to vaccination, no serious adverse reactions were observed.

CONCLUSION CJ-50300 can be used safely and effectively in healthy adults previously vaccinated against smallpox.