THE debate over whether the MMR vaccine can trigger autism and bowel disease
is raging as fiercely as ever, thanks to a controversial study linking these
problems to the measles virus.
MMR first came under suspicion in 1998, when Andrew Wakefield, a
gastroenterologist then at the Royal Free Hospital in London, found that a
handful of children developed autism shortly after their MMR shots. The children
all had bowel problems too. He couldn鈥檛 prove a link, but suggested there was
cause to worry that the vaccine triggered the symptoms.
Since then, numerous epidemiological studies have failed to show any connection
(New Scientist, 3 February 2001, p 8).
That includes a large British study, now being rushed to press in the British Medical
Journal, that looked at 500 children with autism born between 1979 and 1998. In it,
Elizabeth Miller, head of the immunisation division at Britain鈥檚 Public 91色情片
Laboratory Service, found that autistic children who were vaccinated with MMR
were no more likely than the others to have bowel problems. However, the number
of children with these symptoms is so small that critics says these kinds of
survey will never find a link, even if it exists.
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Now a study by John O鈥橪eary at the Coombe Women鈥檚 Hospital in Dublin and his
colleagues, including Wakefield, has come up with a potential link鈥攏ot
with the vaccine, but with measles itself. The researchers examined tissue
samples from 91 children suffering from a new variant of inflammatory bowel
disease called ileocolonic lymphonodular hyperplasia (ILH), and 70 unaffected
children. In a paper due to appear in the April issue of Molecular
Pathology, they report that 82 per cent of the sick children and only 7 per
cent of the controls had measles virus in their gut.
The team did not investigate whether the virus came from a vaccine or from an
infection. Nor have they shown that it caused the bowel disease鈥攊nstead,
the bowel disease could have made it harder for children to clear measles virus
from their systems. But O鈥橪eary speculates that measles could be an
鈥渋mmunological trigger鈥� for ILH.
Bill Bellini, head of the measles virus section at the Centers for Disease
Control and Prevention in Atlanta, Georgia, criticises O鈥橪eary and his team for
not publishing DNA sequence data to show what virus fragments they found. He
adds that he鈥檚 surprised the group detected virus fragments in the tiny amounts
reported.
But Vijendra Singh, a neuroimmunologist at Utah State University in Logan,
says 鈥渢he science is solid鈥�. Singh鈥檚 own work, to be presented next week at a
meeting in Geneva, has found that autistic children have higher than normal
levels of measles antibodies鈥攁nd that the source of the measles is the
vaccine.
What needs to be done now, says Bellini, is to look for genetic markers for a
predisposition to autism. Then these children can be tracked from birth to see
whether those who do experience developmental problems also had an irregularity
with their immune systems at the time of their vaccinations. Until those studies
are done, the debate will stay up in the air.