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HHS Extends Anthrax Postexposure Prophylaxis Options

Kate Traynor

Acting on what he called an "abundance of caution," Health and Human Services (HHS) Department Secretary Tommy G. Thompson yesterday said that some people who were exposed to the bacterium that causes anthrax may want to continue therapy beyond 60 days.

Thompson said that people who were exposed to Bacillus anthracis may wish to continue antimicrobial therapy for an additional 40 days. Another option would be to receive 40 additional days of antimicrobial therapy and three doses of the anthrax vaccine.

A third option offered by Thompson was to stop therapy after the initial 60 days but to remain alert for symptoms that could indicate anthrax infection.

Thompson made the remarks during a teleconference that was also attended by officials from the Centers for Disease Control and Prevention (CDC), National Institutes of Allergy and Infectious Diseases (NIAID), Office of Public Health Preparedness, and Food and Drug Administration (FDA). A transcript of the teleconference is available at

NIAID Director Anthony S. Fauci said during the teleconference that the treatment options were extended based on the results of animal studies in which B. anthracis spores were found to persist in the lungs for up to 100 days.

"Importantly, none of those animals were treated for 60 days," Fauci said, referring to the standard duration of antimicrobial therapy for humans after exposure to B. anthracis spores.

D.A. Henderson, director of the Office of Public Health Preparedness, noted that "we’ve had no cases of anthrax in humans beyond 43 days." He and Thompson both said that the optional precautions might be most appropriate for people who had been exposed to a large number of B. anthracis spores.

Henderson acknowledged that some people who received postexposure antimicrobial prophylaxis suffered from adverse drug reactions. "Taking another 40 days on top of 60 days may be a very unpleasant experience indeed," he noted.

Postexposure use of the anthrax vaccine is not currently approved by FDA, and Thompson said the vaccine would be treated as an investigational new drug in this group of recipients. Patients who choose to be vaccinated would receive three doses of the material over a four-week period and would also receive concurrent antimicrobial prophylaxis.

Kathy Zoon, director of the FDA Center for Biologics Evaluation and Research, said that the major adverse events associated with the anthrax vaccine are edema and redness at the injection site. These symptoms can persist for "days to weeks," she said.

CDC Director Jeffrey P. Koplan estimated that the vaccine could be available by tomorrow but said he did not believe there is an urgent need to move quickly on vaccination.

An HHS press release gives additional details about the extended postexposure treatment options.