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MMR and autism - Denmark


Clinical bottom line

A large survey of all children born in Denmark between January 1991 to December 1998 shows no difference in the incidence of autism between vaccinated and unvaccinated children.


KM Madsen et al. A population-based study of measles, mumps and rubella vaccination and autism. New England Journal of Medicine 2002 347: 1477-1482.


This was a retrospective study of all children born in Denmark between January 1991 to December 1998. In Denmark, a system of unique personal identification numbers, linked to vaccination registers and linked information about the diagnosis of autism makes almost complete follow up possible. A record review of 40 children with autism by a consultant in child psychiatry confirmed that 92% of children met operational criteria for autism.

The national Danish vaccination programme recommends first vaccination at 15 months and again at 12 years.


There were 440,655 children vaccinated, and 96,648 children who were unvaccinated. The mean age of vaccination was 17 months, and 99% of children vaccinated had their first vaccination before they were three years of age. The proportion of vaccinated boys and girls was the same, at 82%.

Table 1 shows the number and percent of children who developed autism or autistic spectrum disorders.

Table 1: Autism and MMR vaccination in Denmark







Number with autism



Percent with autism



Number with autistic spectrum disorder



Percent with autistic spectrum disorder



Using person-years of exposure, there was no statistically significant difference between vaccinated and unvaccinated children for autism (relative risk 0.9, 95% confidence interval 0.7 to 1.2) or autistic spectrum disorders (relative risk 0.8, 0.7 to 1.1). There was no association between development of autism and age at vaccination (95% before two years of age) or the interval between vaccination and development of autism with no clustering at any particular time.


This study provides additional information confirming the lack of any association between MMR vaccination and development of autism. About 1 in 1,700 children developed autism and 1 in 1250 autistic spectrum disorder whether they were vaccinated or not. The prevalence in eight year-olds was 7.7 per 10,000 for autism and 22 per 10,000 for autistic spectrum disorder.