NEW YORK (Reuters Health) – For individuals exposed to anthrax and who have completed 60 days of antibiotic treatment, the US Centers for Disease Control and Prevention (CDC), Atlanta, is offering two additional treatment options for those who want to take additional precautions.

"To date no cases on inhalation anthrax have occurred among the 10,000 people for whom antibiotics have been recommended or offered," Dr. Julie L. Gerberding from the CDC said in a CDC Webcast on Friday. "So while we are looking at additional options, we are not talking about a known hazard, but something that is theoretical," she added.

Whether anthrax remains potent after 60 days of antibiotic therapy and whether addition antimicrobial therapy and vaccination further reduces the risk of inhalation anthrax are not known, Dr. Gerberding said.

"Based on available data, once you are beyond 100 days after exposure, I think you can have an increasing amount of comfort," Dr. Bradley A. Perkins from the CDC said. "I can't guarantee that the risk is zero, but it is vastly diminished."

The first option offered by the CDC is an additional 40 days of antibiotic therapy. This recommendation is based on the possibility that anthrax spores may remain in the body and can cause infection for up to 100 days after the initial exposure.

The second option combines 40 days of additional antibiotic therapy and anthrax vaccination. Anthrax vaccination requires three doses of vaccine given over 4 weeks. Although the Food and Drug Administration has not approved this use of the vaccine, the CDC believes that vaccination may provide additional protection to those exposed to anthrax.

Patients who opt to receive the vaccine will be asked to sign an informed consent form and to be available for a follow-up study to test the effectiveness of the vaccine.

To make a rational recommendation about treatment for individual patients, physicians need to balance what is known about the benefits of these treatments with treatment risks. These decisions now have to be made when there are far too little data to develop firm conclusions and no precise measure of individual exposure risk, Dr. Gerberding said.

Some factors that should be considered to assess the magnitude of risk are the level of exposure and whether any other person in the same environment has developed inhalation anthrax. Patients must also be able to adhere to the treatment regimen, she added.

Right now there is no established time when it is too late for patients to participate in this program, Dr. Perkins noted. "However, I would suggest that people consult their physician and make their decision as rapidly as possible. Because if patients feel they are at increased risk, we would like to give these additional preventive measures as soon as possible."

To oversee the vaccine program, the CDC is sending five teams of scientists and other staff to the sites of anthrax exposure in Florida, Washington DC, New York City, New Jersey and Connecticut. The teams will be working with a medical contractor to give the vaccine and antibiotics to those who want them.

The CDC teams will be responsible for making sure the vaccine is stored and administered correctly and to make sure informed consent forms are signed. They will also note adverse events and be available to answer questions from those who want to be vaccinated.

"We at CDC are acknowledging that we have a lot to learn about the value of any of these therapies, and we are still learning as we go," Dr. Gerberding said.