Tissue-cultured smallpox vaccine shows promise

March 13th, 2009 - 3:27 pm ICT by IANS  

Tokyo, March 13 (IANS) A tissue-cultured smallpox vaccine can show an effective response with no serious adverse events, according to a new study.
“The threat of smallpox bioterrorism has prompted reconsideration of the need for smallpox vaccination. Serious adverse events associated with first-generation vaccines such as the New York City Board of Health (Dryvax), Lister, and Ikeda strains have raised obstacles to vaccination campaigns in the United States,” the study authors wrote.

“Developing a vaccine that is safer than first-generation vaccines yet highly immunogenic (producing immunity or an immune response) is crucial to constructing a prevention plan in the event of bioterrorist attack,” they added.

Tomoya Saito, Keio University, Tokyo, and colleagues examined the clinical and immunological responses to the LC16m8 vaccine in adults who had been previously vaccinated and in those who had not.

LC16m8 is a live, attenuated (reduced in strength), tissue-cultured third-generation vaccine that was administered to more than 100,000 infants in Japan between 1973 and the beginning of 1976.

The adults in this study, who are in the Japan Self-Defence Forces, received the LC16m8 vaccine between 2002 and 2005. Vaccinees were examined 10 to 14 days after vaccination to determine if they had developed a major skin reaction (a measure of immune response, known as take). The researchers monitored vaccinees for adverse events for 30 days after the vaccination.

They found that administration of the vaccine was associated with high levels of seroconversion (development of antibodies) in adults who were not previously vaccinated and yielded an effective booster response in some previously vaccinated individuals, a Keio University release said.

Seroconversion or an effective booster response among the individuals with take was elicited in 37 of 41 (90.2 percent) participants who had not been vaccinated before and in 93 of 155 (60.0 percent) previously vaccinated participants.

The overall proportion of clinical take was significantly higher in primary vaccinees (94.4 percent) than in revaccinees (86.6 percent).

These findings were published in Wednesday’s issue of Journal of the American Medical Association.

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