Evidence that measles-mumps-rubella immunisation is not associated with autism

A UK study published in this week’s issue of THE LANCET provides further evidence that measles-mumps-rubella (MMR) immunisation is not associated with the development of autism or other pervasive developmental disorders (PDDs) in children.

Public concern that MMR vaccination might cause autism has led to a fall in vaccine coverage before age 2 years, from around 92% in 1995-6 to 82% in 2002-3. Liam Smeeth (London School of Hygiene and Tropical Medicine, UK) and colleagues did a ‘case-control’ study to compare the rate of MMR vaccination among children who later developed autism or other PDDs (cases) with children who did not develop PDDs (controls).

Using the UK General Practice Research Database, the investigators studied the records of 1294 cases and 4469 controls; the controls were matched for year of birth, sex, and general practice. The median age of PDD diagnosis was 5.4 years. 78% of cases (1010 children) had MMR vaccination recorded before PDD diagnosis, compared with 82% of controls (3671 children); this difference is not statistically significant. Findings were similar when restricted to children with a diagnosis of autism, to those vaccinated with MMR before the third birthday, or to the period before media coverage of the hypothesis linking MMR with autism.

Dr Smeeth comments “We have found no convincing evidence that MMR vaccination increases the risk of autism or other PDDs. No significant association has been found in rigorous studies in a range of different settings. These are severe diseases for which very little is known about causation; this absence of knowledge itself might have contributed to the misplaced emphasis on MMR as a cause. Research into the real origins of autism is urgently needed.”