In case there were any doubts, a new study indicates that the widespread administration of antibiotics in response to the anthrax attack this past October was a good idea after all. Thus far, the Centers for Disease Control and Prevention has confirmed 11 cases of inhalation anthrax, five of which resulted in death. But a statistical analysis of the U.S. outbreak, published today in the journal Science, indicates that twice as many people could have contracted the potentially fatal inhalation form of anthrax had they not taken antibiotics.

By January of this year, public health officials had recommended that approximately 10,000 potentially exposed people undergo a 60-day regimen of antimicrobial prophylaxis. Roughly half of these individuals worked at or had visited one of three exposure sites: a postal facility in New Jersey, another in Washington, D.C., and the Boca Raton offices of American Media, Inc. Focusing on these patients, Ron Brookmeyer and Natalie Blades of Johns Hopkins University developed a statistical model to estimate the probable number of anthrax cases prevented by prophylaxis, based on information about dates of exposure, symptom onset and the anthrax incubation period. Their analysis clearly shows that the antibiotics saved lives, but Brookmeyer notes that an absence of antibiotics would probably have resulted in only nine additional cases.

In addition to confirming the wisdom of these recent decisions, the study could also influence future public health policy. Brookmeyer says that their finding "demonstrates that earlier intervention and treatment can save lives and must be a critical element of any biodefense strategy."