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Smallpox Vaccine Test Stopped Due to Side Effects

Health Central

Recruitment of volunteers to test a new smallpox vaccine has been halted early after participants developed significant heart inflammation, the Washington Post reported.

While biodefense contractor Acambis PLC said it would continue to study those who had already been given the experimental vaccine, it said it would no longer administer the inoculation to new recruits, the newspaper said.

The trials had been conducted to test the Acambis product, ACAM2000, versus Dryvax, a smallpox vaccine that has long-since been approved. The company said three participants among the 1,132 volunteers who had been given either vaccine experienced heart inflammation -- at least one coming from the group testing the newer shot, the Post reported.

A spokesman for the U.S. Centers for Disease Control and Prevention told the newspaper he didn't know what effect the announcement might have on the government's plans to use more than 200 million doses of ACAM2000 it has stockpiled in the event of a bioterrorist attack -- enough for every American.

The newer product is a modernized version of Dryvax, and experts had predicted the two vaccines might share some harmful side effects, the newspaper reported. A leading government health official called the initial stockpile a "stopgap" until a safer alternative became available.