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Third-Generation Smallpox Vaccine LC16m8 Deemed Effective

In unvaccinated or previously vaccinated adults, it's associated with a high level of immunogenicity

TUESDAY, Mar. 10 (HealthDay News) -- In unvaccinated or previously vaccinated adults, the use of the third-generation smallpox vaccine LC16m8 is associated with a high rate of seroconversion or booster response, and a low rate of adverse reactions, according to research published in the Mar. 11 issue of the Journal of the American Medical Association.

Tomoya Saito, M.D., of Keio University in Tokyo, Japan, and colleagues administered LC16m8 to 1,529 unvaccinated adults and 1,692 previously vaccinated adults in Japan's Self-Defense Forces, and assessed them at 10 to 14 days to see if they developed a major skin reaction, or "take." They also followed the subjects for 30 days to monitor adverse reactions.

The researchers observed a "take" in 1,443 (94.4 percent) of the unvaccinated adults and in 1,465 (86.6 percent) of the previously vaccinated adults. In a subset of 196 subjects with "take," they found that seroconversion occurred in 90.2 percent of unvaccinated subjects and an effective booster response occurred in 60 percent of previously vaccinated subjects. The investigators observed two mild, self-limiting reactions, including one case of allergic dermatitis and another of erythema multiforme, but no serious adverse reactions.

"LC16m8 vaccine appears to be a viable alternative to first-, second- and other third-generation vaccines in a smallpox preparedness program," the authors conclude.

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