Providing antibiotics quickly to people exposed to deadly anthrax spores in a bioterror attack could prevent the vast majority of infections, according to a new study by researchers at the Johns Hopkins Bloomberg School of Public Health.
If individuals start treatment within six days of exposure to the bacteria, the prevention rate would be about 70 percent, the scientists found.
Beginning an antibiotic course even sooner - within three days - would raise the prevention rate to well over 80 percent.
"A targeted and rapid response to an anthrax attack is essential," said Ron Brook-meyer, professor of biostatistics at the School of Public Health and the lead author of the study, published in today's issue of the journal Nature.
From their statistical model - based on what's known about current and future anthrax treatments - Brookmeyer and his colleagues also found that a new, more effective vaccine administered after an attack could significantly shorten the length of time patients would need to remain on antibiotics.
Although vaccines are typically given before exposure to create immunity, inoculation soon afterward can afford protection because of a disease's incubation period.
Brookmeyer said that for those exposed to a high dose of anthrax, a new vaccine could shave up to 43 days from a burdensome four-month course of treatment.
"That's important because of adherence problems with antibiotics," he said.
During the 2001 anthrax scare, in which five people died, less than 50 percent of those who received antibiotics completed the prescribed regimen, he said, although none of those who stopped subsequently became ill.
Even so, cutting antibiotic treatment short worries health officials: It can leave some bacteria alive and resistant to future treatment.
As part of its effort to prepare the nation for possible germ warfare - dubbed Project BioShield - the federal government last month ordered nearly $900 million worth of a new-generation anthrax vaccine being developed by VaxGen.
Under the five-year contract, the California-based pharmaceutical firm will provide enough doses to immunize about 25 million people.
The only anthrax vaccine currently licensed in the United States, which is administered in six shots over 18 months, has been the subject of considerable debate in recent years. Critics have questioned its effectiveness and argued that it can cause serious side effects in some patients.
In response to a suit filed by six unidentified plaintiffs serving in the military, a federal judge ordered the Defense Department in October to halt its mandatory anthrax vaccination program. Soldiers who sign a consent form may still be immunized.
The new VaxGen vaccine, which has yet to be approved by the Food and Drug Administration, is expected to consist of three shots or fewer and provide immunity more quickly.
Dr. Tyler C. Cymet, head of family medicine at Sinai Hospital in Baltimore and assistant professor of medicine at Hopkins' School of Medicine, treated a patient in 2001 who became seriously ill after exposure to anthrax-laden dust at the contaminated Brentwood postal facility in Washington, D.C.
He has also conducted follow-up interviews with survivors to monitor how their symptoms have progressed.
Cymet said that the new study provides information that could help physicians better treat exposed individuals - should there be an attack.
"It could be a major catastrophe if there's a release [of anthrax], so how do we prevent it?" he said. "It looks like we could avert a major catastrophe and defuse an anthrax bomb with antibiotics."
The Centers for Disease Control and Prevention in Atlanta, the nation's top public health agency, does maintain a stockpile of such drugs, along with vaccines and medical supplies, for use in the event of a bioterror attack or other national emergency.