The latest Medical Research Council study of more than 5,000 UK children has ruled out any link between MMR, the measles, mumps and rubella triple vaccine, and autism. Ministers and health chiefs have pronounced it the most “authoritative” and “comprehensive” study yet and said it should be “the last word in the debate”.
Similar things were said two years ago about Danish research into the
vaccination history of more than 500,000 children, published in the New
England Journal of Medicine. It was also said to show no link. Yet earlier
this month two separate reviews of the Danish records, published in the
Journal of American Physicians and Surgeons, have come to the opposite
conclusion, citing significant increases in autism in Denmark since MMR was
introduced.
How could the conclusions be so different? Mainly because in Denmark
autism is often diagnosed later, at the age of five, and the original Danish
paper only tracked the children for four years, thus missing cases.
The first new paper, by American paediatrician Fouad Yazbak, looked
at levels of autism from 1980 – six years before the MMR vaccine was
introduced – until 2002. It found that autism rates in children aged five to
nine were just over 8 per 100,000 in the years before MMR was introduced;
but by 2000 it had risen to just over 7 L cases per 100,000.
Unlike the new MRC paper, this one received scant attention in the UK
press. The British Medical Journal said it did not cover the study because
it did not know how reliable it was.
The second review, also in the Journal of American Physicians and
Surgeons, received little attention either. But then one of its authors was
Dr Andrew Wakefield, the controversial gastroenterologist at the centre of
the debate in the UK. His review, with Dr Carol Stott, a Cambridge
psychologist and autism expert, showed autism cases in Denmark have
increased steadily by 14.8 percent each year since the introduction of MMR.
Both studies suggest only some of the increase is accounted for by better
and wider diagnosis.
Meanwhile challenges to the assumptions of the MRC’s “last word”
study have already started. That study looked at the vaccination records of
1,294 children diagnosed with autism, compared them with 4,469 children of a similar sex and age and concluded that “normal” children were as likely to
have had the jab as autistic children. The week after it was published in
the Lancet, delegates gathered in Denmark for the World Autism Organisation’ s annual conference. Though the MRC paper was not on the agenda, MMR and the shortcomings of epidemiological studies in the debate were.
The first criticism is one that is levelled at epidemiological
studies on both sides of the debate. It is said that they lump all autism
and pervasive developmental disorder together, which is akin to searching
for an increase in a particular type of cancer but including the results for
all cancers. No one has ever suggested that MMR is responsible for all
autism.
The suggestion is that it might be a factor in a sub-group of children with
regressive autism and bowel disease.
The MRC study is further undermined, it is claimed, because at the
time it was made around 80 percent of those whose records were examined had received the MMR vaccine, making it difficult to evaluate the outcome in
sufficient numbers for unvaccinated children. Critics suggest that more
children needed to be included in the study.
The Danish conference also heard evidence from Dr Stott, who has been
looking specifically at the children involved in the stalled litigation in
the UK against the vaccine manufacturers. Although her study so far is very
small -just 94 children – and not conclusive, she reported that there may be
an association between specific brands of MMR and a particular behavioural
presentation in the autistic children, whose onset comes shortly after
vaccination and is characterised by severe and pervasive developmental
regression and gut disease.
Most, although not all, of the children who were also found to be
more likely to have measles virus in their bloods had had the earlier forms
of MMR, which were withdrawn because they caused aseptic meningitis.
Although those brands of vaccine are no longer on the market, there were
still small but significant numbers of children with similar regressive autism who had had the newer vaccines. The researchers had alerted the department of health to their findings back in February this year, suggesting the need for further investigation. So far they have only received an acknowledgement of receipt of their letter.
The debate, then, is far from over. With some scientists relying on
population studies and others looking at the children involved in the
claims, it is like comparing chalk with cheese and parents are still confused, sceptical and concerned. With uptake of MMR last week reported to be around 80 percent, it is unfortunate that researchers on both sides of the debate cannot work together.
While research to find out what children with autism have in common
has all but stopped in Britain, it continues in the US. In particular,
scientists and doctors there are looking to see if the findings of vaccine-strain measles virus at the site of the diseased guts of autistic children can be replicated. The results of these studies – which should have been done years ago when Dr Wakefield and others first reported the findings- are expected later this year.