No evidence for links between autism, MMR and measles virus

Chen W, Landau S, Sham P, Fombonne E.
Institute of Psychiatry, King's College and Department of Child and Adolescent Psychiatry, Guy's, King's and St Thomas's School of Medicine, University of London.

Abstract: Psychol Med. 2004 Apr;34(3):543-53

Findings

Reports of a temporal association between the onset of autistic symptoms, gastro-intestinal symptoms and immunization with measles-mumps-rubella (MMR) vaccines raised concerns of measles and MMR as risk factors for autism. However, several large epidemiological studies on autism disorder (AD) and MMR have not detected any significant link. Dr. Chen and his colleagues examined if there was an increased risk of autism following early-life exposure to (1) wild measles, (2) live attenuated measles, alone or in combination with MMR, and (3) altered mumps strain within MMR vaccine. The researchers examined 2,407 subjects with autism disorder born between 1959-1993 and compared them with 4,640 Down’s syndrome (DS) subjects born between 1966–93. Between 1968–86, the researchers correlated variations in AD and DS births with the incidence of wild measles. Between 1959–93, they tested for abrupt changes in the trends in long-term AD birth and correlated any changes with the effects of introducing: (1) wild measles vaccines in 1968; (2) MMR immunization in 1988; and (3) the sudden switch in 1992 from mixed use of Urabe MMR to exclusive use of Jeryl–Lynn MMR. They found no significant association between AD births and exposure (prenatal and postnatal up to 18 months age) to population rates of measles infections, and no increase in AD births associated with the introduction of monovalent (wild) measles and MMR vaccines, and changing mumps strain. In this study, Dr. Chen found an unexpected 21% reduction in AD births among the post-1987 birth group examined.

Conclusions

Despite isolated reports of the onset of symptoms of autism with the introduction of the MMR vaccine in some individuals, these results indicate that there is no increased risk of AD after exposure to wild measles and vaccinations with monovalent measles or variants of the MMR vaccines. The finding of the reduction in AD births among the post-1987 birth group was not clear.