Animal experiments have confirmed the prolonged persistence of spores and incubation period after aerosol exposure. In one study, rhesus macaques were protected during a 30-day course of antibiotics after aerosol exposure. However, some animals developed fatal infection after the antibiotic therapy was discontinued.
"In spite of the low compliance rates we saw in 2001--where more than half of the people did not take the full 60-day course--there were no additional anthrax cases," Friedlander commented. "This suggests that the doses of inhaled spores were probably very low. In contrast, computer modeling suggests that protection against higher doses of anthrax spores could require that antibiotics be continued for as long as four months. Adding vaccine to a postexposure regimen of antibiotics may shorten the duration and thus avoid the problems of noncompliance associated with a prolonged course."
Colonel George W. Korch, Jr., USAMRIID commander, added, "The tremendous value of interagency collaboration cannot be understated in this very important finding, which stands to potentially improve the course of therapeutic intervention, as well as enhance overall protection against this significant biological threat."