Safe in the woods


By Alison Motluk CAMPERS and walkers may soon be able to walk in the forest without worrying about catching Lyme disease—one of the fastest-spreading infectious diseases in the US. Cases of Lyme disease, carried by ticks that live on forest-dwelling animals such as deer, have increased 32-fold in the US since 1982, with over 10 000 reported last year alone. But last week an advisory committee to the US Food and Drug Administration (FDA) recommended that a new vaccine should be approved for commercial use. If spotted early, Lyme disease will usually respond to an intensive course of antibiotics, but initial symptoms are sometimes difficult to recognise. While about two-thirds of sufferers develop the hallmark “bull’s eye” red rash, other early signs are practically indistinguishable from flu. The full-blown illness can be severe or even fatal, sometimes involving chronic arthritis, heart problems and meningitis. The disease is transmitted when an infected tick feeds on blood from a human and passes on the spirochaete bacterium Borrelia burgdorferi. Approximately 35 per cent of ticks in the US are infected, according to the Centers for Disease Control and Prevention in Atlanta. The figure is 50 per cent in some regions. And in some parts of Europe 90 per cent of ticks are affected, although the disease-causing spirochaete is a slightly different strain and may not be affected by the new vaccine. The vaccine, developed by SmithKline Beecham, produces antibodies that target a surface protein on the bacteria, killing them while still in the tick’s gut. Over 10 000 people took part in the company’s clinical trial, which found that the vaccine provided on average 79 per cent protection. Among people under the age of 65, however, it gave 90 per cent protection. The vaccine has to be given in three doses—the first is followed by another a month later and a third at the end of a year. After the first two jabs, the vaccine was still only 50 per cent effective. Even after the full three doses, protection was only shown to last 20 months, and SmithKline Beecham has not ruled out the possibility that the vaccine may have to be topped up every year. “That’s something we still have to look at,” says Rick Koenig, a spokesman for the company. The FDA committee has not yet approved boosters to supplement the first three jabs. Pat Nuttall, an expert on Lyme disease at the Institute of Virology in Oxford, says: “Normally a vaccine with those kinds of properties wouldn’t be passed, but they’re so desperate.” Caroline Hall of the University of Rochester School of Medicine and Dentistry in Rochester, New York, a member of the FDA committee, says that although the committee supports the vaccine, there were some concerns about its efficacy beyond 20 months, the safety of annual boosters and whether it could be used safely in children. “They don’t have data for the paediatric age group,” she says. “And there were very few teenagers in the trial.” However,
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