CAMPERS and walkers may soon be able to walk in the forest without worrying
about catching Lyme disease鈥攐ne 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 鈥渂ull鈥檚 eye鈥� 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.
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The vaccine, developed by SmithKline Beecham, produces antibodies that target
a surface protein on the bacteria, killing them while still in the tick鈥檚 gut.
Over 10 000 people took part in the company鈥檚 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鈥攖he 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. 鈥淭hat鈥檚 something we still have to look at,鈥� 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: 鈥淣ormally a vaccine with those kinds of properties wouldn鈥檛 be
passed, but they鈥檙e so desperate.鈥�
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. 鈥淭hey don鈥檛 have data for the paediatric age group,鈥� she
says. 鈥淎nd there were very few teenagers in the trial.鈥�
However, SmithKline Beecham is planning a trial in which 3000 children will
be given the vaccine next year.