IT IS the classic bioterror nightmare 鈥� tonnes of lethal anthrax spores dumped on a city. So scary in fact, that last month the US government announced a $877 million contract for VaxGen, a small Californian company, to make a stockpile of 75 million doses of a vaccine that has not yet been fully tested or licensed.
But Ron Brookmeyer of Johns Hopkins University in Baltimore says vaccination might be of little use after an anthrax attack (Nature, vol 432, p 901). His statistical model reveals that simply giving antibiotics as soon as possible would work best 鈥� preventing up to 75 per cent of the cases that would have happened without intervention. If people do not take all their tablets, as happened after the 2001 anthrax attacks in the US, that figure drops to 65 per cent.
鈥淓ven vaccinating before attacks doesn鈥檛 help unless you get to most people鈥�
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In the model, mass vaccination after an attack only prevented 6 per cent more cases than partial antibiotic treatment, although it might theoretically protect against spores that persist, either in the lungs or the environment, after drug treatment stops. Even vaccinating before the attack doesn鈥檛 help prevent many cases unless you get to most people. At least two-thirds need to have been vaccinated before survival rates are much better than with antibiotics alone.
