MMR CAUSE

Does MMR Cause Autism?

Does MMR Cause Autism?

The Mumps/Measles/Rubella (MMR) vaccine uses several live viruses to immunize children against what have, in the past, been disabling and even fatal illnesses. In 1994, the vaccine was mandated for all school age children. Since then, a spike has been seen in autism diagnoses. Many of those diagnoses occur within months of children's first MMR shot. Is there a connection? Despite energetic denials by major research institutions, the question remains controversial.

The study of Mumps/Measles/Rubella provides three strong arguments against a causal relation between MMR vaccination and autism. First, the risk of autism was similar in vaccinated and unvaccinated children, in both age-adjusted and fully adjusted analyses. Second, there was no temporal clustering of cases of autism at any time after immunization. Third, neither autistic disorder nor other autistic-spectrum disorders were associated with MMR vaccination. Furthermore, the results were derived from a nationwide cohort study with nearly complete follow-up data.

All previous studies of an association between autism and MMR vaccination have been case series,1,14,15 ecologic studies,11,12 or cross-sectional studies,10,13 and the majority have not used optimal data for risk assessment. In a well-conducted, cross-sectional prevalence study, Taylor and colleagues found that there was no sharp increase in the prevalence of autism after the introduction of the MMR vaccine. However, it could be argued that a more gradual increase would be expected, since autism is characterized by an insidious onset and a delay in diagnosis. A case-series study by Peltola et al.15 also provides evidence against a causal connection.

One of the main reasons for public concern has been that the widespread use of the MMR vaccine in some regions appeared to coincide with an increase in the incidence of autism. However, this is not a uniform finding. In Denmark, the prevalence of autism (according to the criteria of the International Classification of Diseases, 8th Revision) was less than 2.0 cases per 10,000 children between the ages of five and nine years in the 1980s and the beginning of the 1990s. Since then, the rates have increased in all age groups except for children younger than two years of age, and in 2000, the prevalence of autism (according to the ICD-10 criteria) was higher than 10.0 cases per 10,000 children five to nine years of age (unpublished data). Thus, the increase in autism both in California5 and in Denmark occurred well after the introduction of the MMR vaccine.

MMR is based on individual reports of vaccination and diagnoses of autism in a well-defined geographic area. The exposure data were collected prospectively, independently of parental recall and before the diagnosis of autism. Furthermore, the diagnosis was recorded independently of the recording of MMR vaccination. Thus, there was little possibility of differential misclassification of exposure or outcome measures. Furthermore, our analysis was based on complete follow-up data.

Wakefield was asked to leave his position in Britain, and retracted some of the study outcomes. Today, he is the head of a Texas-based research group called “Thoughtful ...