There is no link between the controversial MMR jab and autism, according to the largest ever published study on the issue.
Fears over an association between the two in the late 1990s led to a drop in the number of children having the jab for mumps, measles and rubella.
Research on 12 children published in the medical journal The Lancet in 1998 suggested a link between the vaccine, autism and bowel disease.
Lead author Dr Andrew Wakefield is currently appearing before the General Medical Council on charges relating to the claims.
Today’s research involved a sample of almost 250 children aged between 10 and 12, born between July 1990 and December 1991 in the South Thames area of England.
The experts noted that two previous studies have reported raised concentrations of measles antibodies in children with autism spectrum disorders (ASD).
Their study sought to find out if this was true.
The experts said they wanted to ‘test the hypothesis that measles vaccine was involved in the pathogenesis of ASD, as evidenced by signs of a persistent measles infection or abnormally persistent immune response shown by circulating measles virus or raised antibody titres in MMR-vaccinated children with ASD compared with controls.’
The study was published in the journal Archives of Disease in Childhood.
It followed 98 children who had an autism spectrum disorder and two comparison groups: 52 children with special educational needs but no evidence of autism spectrum disorder, and 90 children who were normal.
All the children had been vaccinated against MMR, but not all of them had been given both the doses needed for maximum immunity.
Blood samples were taken from all the children to check for the presence of persistent measles infection or an abnormal immune response.
This was indicated by a circulating measles virus or increased antibody levels.
The results showed there was no difference in virus or antibody levels between children with ASD and the comparison groups.
This finding was unaffected by whether or not the child had received both MMR doses or whether or not they had regressed (where children appear to develop communication skills, but then regress).
However, children with special educational needs and those with autism were least likely to have received the second dose, perhaps because their parents refused the second dose after their child developed abnormal symptoms.
The study also found no evidence of bowel symptoms (enterocolitis) among the autistic children, irrespective of whether or not they had regression.
The researchers included experts from Guy’s and St Thomas’ NHS Foundation Trust in London, King’s College London, Manchester University and the Health Protection Agency (HPA).
They concluded: ‘No difference was detected in the distribution of measles antibody or in measles virus in ASD cases and controls whether the children had received the first, second or both MMR vaccinations.
‘This remained true when the analysis was restricted to ASD cases with a history of regression. Only one child had symptoms of possible enterocolitis, and this child was in the control group.’
The prevalence of autism spectrum disorders ranges from six to 12 cases per 1,000 children, depending on how they are diagnosed.
Professor David Salisbury, director of immunisation at the Department of Health, said: ‘It’s natural for parents to worry about the health and well-being of their children and I hope that this study will reassure them that there is no evidence linking the MMR vaccine to autism.’
Dr David Brown, from the HPA who worked on the research, added: ‘The study found no evidence linking MMR to autistic spectrum disorder and the paper adds to the overwhelming body of evidence from around the world supporting the use of MMR.
‘Public confidence in the MMR vaccine continues to remain high as the uptake for those receiving their first dose has stayed stable.
‘However, it is also important to remember that children should complete their full course of MMR vaccine or optimum protection.’
Babies are given the first dose of MMR when they are around 13 months old and the second jab between the ages of three-years-four-months and five, according to the Department of Health.
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