|
|||||
|
|||||
|
|
|
|
|
|
|
|||||
 |
 |
    |
|
|
|||
 |
|
||
|
|||
|
|
|
|
||||||||
|
Rapid Deployment of Antibiotics, Vaccines Would Offer Best Protection in Anthrax Attack, Researchers Say By Chris Schneidmiller WASHINGTON — A “targeted and rapid” deployment of antibiotics and vaccines after an anthrax attack would more effectively protect victims from illness than a mass inoculation program implemented before a potential incident, Johns Hopkins University researchers said this week (see GSN, Dec. 13). The researchers developed a probability model to consider the prevention rates achieved by a preventive vaccination campaign or the use of antibiotics after an attack. Those methods alone had significant drawbacks, but the medicines could work well in tandem as part of a quick response to an outbreak, according to a paper published in today’s issue of Nature. Lead author Ron Brookmeyer said he hoped his work with colleagues Elizabeth Johnson and Robert Bollinger could offer direction to government agencies in developing the best methods to counter an anthrax attack. “I would hope that this work could help form public policy considerations and could help determine where to put limited resources,” Ron Brookmeyer, a biostatistician in the university’s Bloomberg School of Public Health, said yesterday in an interview. Using their mathematical model, the researchers calculated the chances of anthrax spores surviving to germinate within a set of victims and then “forecast what would happen under different public health policies,” Brookmeyer said. Anywhere from 67 to 76 percent of victims of anthrax attack in the model would not become ill if they began taking antibiotics within six days and continued to take the medicine for the recommended period of at least 60 days. “Is 70 percent good enough? If we could get it to people quick enough we could prevent even more cases,” Brookmeyer said. However, prevention rates in the model fell to less than 50 percent if antibiotics were not delivered until 10 days after exposure. Some U.S. postal workers exposed to tainted letters during the 2001 anthrax attacks did not begin treatment for nine days; two of those employees were among the five people who died following infection. The mail attacks to date have been the only real-life test of the U.S. response capability, leaving it difficult to gauge how quickly local, state and federal health agencies are prepared to detect and respond to a biological attack, Brookmeyer said. Rates of success also dropped if the model victims stopped taking the drugs before 60 days. Brookmeyer and his colleagues acknowledge that adherence to the treatment regimen could be a problem — less than half of 10,000 people who were potentially exposed to anthrax in 2001 completed their antibiotic treatment. None of the 10,000 contracted anthrax, indicating they were not exposed, took all their antibiotics or possibly came into contact with a low dose of inhaled spores, Brookmeyer said. There is no assurance that future incidents would involve weak spores. The United States is pouring more than $800 million into production of a new anthrax vaccine under the Project Bioshield program. The planned stockpile would be enough to protect 25 million people (see GSN, Nov. 5). Even in the event that agencies could predict the site of an incident before it occurred, preventing significantly more than 70 percent of anthrax cases would require a potentially unmanageable mass vaccination program The researchers determined that achieving a 90-percent prevention rate among those exposed to the spores would require prevaccinations of 63 percent of “the population you want to protect” — whether it is a neighborhood, a city or the entire country, Brookmeyer said. That vaccination percentage in the model is based on low levels of exposure to anthrax and a rapid post-event response with antibiotics. Higher levels of exposure, a slower treatment response and failure to complete the antibiotic schedule drove the percentage of the population that would need to be vaccinated as high as 95 percent — higher than the percentage of attack victims in the model who would then theoretically not contract the disease. “A mass preattack vaccination program is probably not the best use of resources,” Brookmeyer said. “There is still a place for an anthrax vaccine and one of the places is in shortening the antibiotic regimen.” Administering a vaccine after an incident could complement spore-killing power of antibiotics, researchers said. The existing vaccine, though, would be of limited value as it requires up to six doses over 18 months and might not take effect until the antibiotics regimen is over, Brookmeyer said. The vaccine now being developed is hoped to involve only three doses over 28 days, the researchers said. In the model it boosted the prevention rate anywhere from 1 to 9 percent when applied after an attack. A new vaccine with a shorter inoculation schedule also could help overcome a strain of anthrax resistant to antibiotics and reduce the amount of time a victim would need to use the antibiotics, increasing the likelihood of maintaining the treatment regimen. “Shortening a long course of antibiotics may be critical because of difficulty in maintaining adherence, limited supplies of antibiotics, resistance and adverse events associated with long-term antibiotic therapy,” the research paper says. There are many variables that will determine the success of a response, and variables within each component. The rapidity of the response, for example, with depend on health-care workers’ awareness of symptoms of anthrax infection, communication and coordination between health agencies, the time it takes to put together a treatment plan and the availability of medicines. The U.S. Strategic National Stockpile has enough vaccines and antidotes to respond to an outbreak, and is stored around the country to enable delivery to any site within 12 hours, said Von Roebuck, a spokesman for the Centers for Disease Control and Prevention. The federal health agency has also been teaching local departments on preparing clinics in case of an outbreak. “I think all of this needs to be integrated together and there are lots of things that go into this response,” Brookmeyer said.
| ||||||||||
Back to top
