Study shows no link between MMR vaccination and autismBMJ 2004; 329 doi: http://dx.doi.org/10.1136/bmj.329.7467.642 (Published 16 September 2004) Cite this as: BMJ 2004;329:642
The measles, mumps, and rubella vaccine (MMR vaccine) is not associated with increased risk of pervasive developmental disorders—including autism—according to a case-control study that has confirmed the findings of previous studies (Lancet 2004;364:963-9).
The case-control study used the UK general practice research database—a large database of patients' electronic clinical records—to identify 1294 people born in 1973 or later who had been diagnosed as having a pervasive developmental disorder recorded between 1987 and 2001. Full medical records—including hospital clinic letters and specialist reports—were checked for more than 300 of these people, and the diagnosis was confirmed in more than 90% of the group. They were matched to controls who did not develop this type of disorder, based on age, sex, and general practice.
Results showed that 78% (1010/1294) of cases, who were diagnosed with pervasive development disorder, had been given the MMR vaccine, but a higher proportion (3671; 82%) of controls, without such a disorder, had been given the vaccine.
The odds ratio for association between having the MMR vaccine and having a pervasive development disorder was 0.86 (95% confidence interval 0.68 to 1.09), indicating no relationship. Findings were similar when restricted to children diagnosed with autism, to children vaccinated before their 3rd birthday, or to the period before media coverage in 1998 of the hypothesis linking the MMR vaccine with autism.
One of the researchers, Liam Smeeth, senior lecturer in clinical epidemiology at the London School of Hygiene and Tropical Medicine, London, said, “We found no convincing evidence that MMR vaccination increases the risk of autism or other pervasive developmental disorders.” He considered that the strengths of the study included its large size—more than 1000 cases of pervasive developmental disorder—and the use of population based data.
Vaccination was recorded before the date of diagnosis, so there was no scope for recall bias. In addition, the study allowed examination of data recorded before the hypothesis that MMR increased the risk of autism had been proposed.
The study, funded by the UK Medical Research Council, showed a similar lack of association between MMR vaccination and autism as previous studies in the United States and Scandinavia, based on systematic review. Dr Smeeth reported, “A pooled estimate of all of these studies—carried out in different settings—showed no link between MMR and autism. We can now move on and look for the real causes of autism.”
He considered that the focus on MMR and autism had potentially hampered research into pervasive developmental disorders: “These are severe diseases for which very little is known about causation; this absence of knowledge might itself have contributed to the misplaced emphasis on MMR as a cause. Research into the real origins of autism is urgently needed.”