No link found between MMR and autism in large comprehensive MRC study

A Medical Research Council (MRC) funded study, published in this week's edition of The Lancet, has provided the most detailed and comprehensive assessment to date of the measles-mumps-rubella (MMR) vaccine and autism. It concludes that there is no evidence to support a link between MMR and the subsequent development of autism.

Currently fewer than 82 per cent of children in the UK are being given MMR, reflecting public uncertainty about its safety. Vaccination is now below the level needed to avoid epidemics of measles, which remains a potentially life-threatening infection.

The research team, based at the London School of Hygiene and Tropical Medicine, analysed the medical records of children registered with hundreds of general practices across England and Wales to find out whether those with autism, or other pervasive development disorders (PDDs)*, were more likely to have received MMR. They compared the vaccination histories of 1294 children diagnosed with these disorders between 1987 and 2001 with 4469 'control' children of the same sex and similar age who were registered with the same practices but who did not have a recorded diagnosis of autism.

The authors were unable to find any evidence to support an association between MMR vaccination and autism or other PDDs.

They tested this conclusion by carrying out further analyses which looked only at children who received MMR before their third birthday (autism is not normally diagnosed before age three), and at children vaccinated in the period before reporting of the theory that MMR might be linked with autism. They also compared children who joined the practices before their first birthday with those joining after this age. The conclusion - that there is no link between MMR and autism - remained unchanged following these extensive analyses.

The research team also carried out a systematic review of previously reported studies that examined the possibility of a link. None of these studies - taken alone or in combination with the current MRC study - showed any increased risk of autism associated with MMR. This combined result increases the strength of the assessment that there is no evidence of a link between MMR and autism.

Dr Liam Smeeth, one of the lead scientists, said:

"We hope the results of this study, the most robust and comprehensive undertaken to date, will reassure parents that MMR is not associated with an increased risk of developing autism.

"Our findings are consistent with evidence from a growing body of high quality scientific studies. It is now time to move on and focus on research into other potential causes of autism which is urgently needed"


For more information, or to arrange an interview, contact the MRC Press Office on 020 7637 6011.

Notes to Editors

* Autism and pervasive developmental disorders are defined by early emerging impairments in socialisation and communication, with repetitive and restricted interests and activities. See MRC review (cited below) for further discussion of the clinical features.

The prevalence of autism spectrum disorders was examined in the MRC Review of the Epidemiology and Causes of Autism: The Review found that overall, 60 in 10,000 children under eight years of age have autism.

To take forward the recommendations of the Review, in July 2004 the MRC announced funding for four high-quality research projects to study autism and its potential causes:

Measles, mumps and rubella are not the mild diseases they are commonly perceived to be. About one child in every 15 with measles infection will suffer serious complications like pneumonia and convulsions. About one in 5,000 will get encephalitis - inflammation of the brain - and about the same number will die.

Before vaccination, viral meningitis caused by mumps was one of the biggest causes of child hospital admissions. Mumps killed around five people a year in the UK. Rubella is a mild illness for children, but can have dreadful consequences for a pregnant woman's unborn child. Rubella virus can spread to infect every part of the fetus causing devastating brain damage, deafness and blindness.

The Medical Research Council (MRC) is a national organisation funded by the UK tax-payer. Its business is medical research aimed at improving human health; everyone stands to benefit from the outputs. The research it supports and the scientists it trains meet the needs of the health services, the pharmaceutical and other health-related industries and the academic world. MRC has funded work which has led to some of the most significant discoveries and achievements in medicine in the UK. About half of the MRC's expenditure of over £413 million is invested in its 40 Institutes, Units and Centres, where it employs its own research staff. The remaining half goes in the form of grant support and training awards to individuals and teams in universities and medical schools. See also their website:

The London School of Hygiene & Tropical Medicine is a renowned research-led postgraduate medical school with a unique mission: to contribute to the improvement of health worldwide through the pursuit of excellence in research, postgraduate teaching advanced training and consultancy in international public health and tropical medicine.

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