Diluted Smallpox Vaccine Found Effective

Current U.S. stockpile can be expanded if needed, study finds

TUESDAY, Sept. 7, 2004 (HealthDayNews) -- Diluting smallpox vaccine that is more than 50 years old is almost 100 percent effective, which means the current U.S. stockpile can be expanded if needed, a new study found.

Researchers at Vanderbilt University School of Medicine in Nashville, Tenn., injected 340 healthy volunteers with three different strengths of the Aventis Pasteur smallpox vaccine (APSV) -- undiluted, one-to-five dilution, or one-to-10 dilution.

The vaccine was originally manufactured in the 1950s and stored as a frozen preparation.

Those who received the undiluted vaccine had a 100 percent successful vaccination rate. Those who received the one-to-five dilution had a 98.2 percent success rate, and those who received the one-to-10 dilution had a 100 percent success rate, the study found.

"The results of our study show that a frozen preparation of APSV has a high vaccination success rate and is an available option for smallpox vaccination of vaccinia-naive persons, even at ten-fold diluted doses. This allows for amplification of the current smallpox vaccine stockpile (approximately 85 million doses of APSV), if needed," the study authors wrote.

The report appears in the Sept. 8 issue of the Journal of the American Medical Association.

More information

The U.S. Centers for Disease Control and Prevention has more about smallpox and smallpox vaccine.

SOURCE: Journal of the American Medical Association, news release, Sept. 7, 2004
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