There is no evidence for a link between the MMR (measles, mumps, rubella) jab and autism, finds research published ahead of print in the Archives of Disease in Childhood.
MMR has been linked to the development of autism, following the publication in 1998 of research on 12 children, which has since been discredited.
The prevalence of autism spectrum disorders ranges from 6 to 12 cases per 1000 children, depending on how the diagnostic criteria are applied.
The findings are based on a community sample of almost 250 children aged between 10 and 12, born from a population of 57 000, born between 1990 and 1991 in one area of Southern England.
The sample comprised 98 children who had an autism spectrum disorder, and two comparison groups: 52 children with special educational needs, but no evidence of autism spectrum disorders, and 90 children who were developing normally.
Some of the children with autism had experienced a set-back or regression early in their development.
All the children had been vaccinated against MMR, but not all of them had been given both doses.
Blood samples were taken, to check for the presence of persistent measles infection, or an abnormal immune response, indicated by circulating measles virus or increased antibody levels.
Results of the blood sample analysis showed that there was no difference in circulating measles virus or antibody levels between the two groups of children.
This finding was not affected by whether or not the child had received both MMR doses or whether or not they had regression.
Furthermore, there was no evidence of bowel symptoms (enterocolitis) among the autistic children, irrespective of whether or not they had regression.
Children who were autistic and those with special educational needs were less likely to receive the second dose of MMR, possibly reflecting parental concern about vaccination following the diagnosis of a developmental abnormality.
The authors point out that theirs is now the third, and largest, study that has failed to show a link between the MMR jab and autism.