Andrew Wakefield made two blunders, one widely publicised, the other, scarcely mentioned, yet worse.A Danish study of more than half a million children showed no link between measles, mumps, and rubella (MMR) vaccination and autism.
In a commentary accompanying the study, which was published in the , Dr Edward Campion, senior deputy editor, wrote, “This careful and convincing study shows that there is no association between autism and MMR vaccination.”
Lead author Dr Kreesten Meldgaard Madsen, an epidemiologist and expert on infectious diseases at the Danish Epidemiology Science Centre in Aarhus, told the BMJ that the study showed that the risk of autism was similar in children who were vaccinated and children who were not.
The study reviewed records of 537303 children born in Denmark between January 1991 and December 1998, representing almost 100% of children born in that period. Of these children 440655 had been vaccinated. Records were retrieved from three sources: the unique identification number assigned to each child at birth; MMR vaccination data reported to the National Board of Health by general practitioners, who give all MMR vaccinations and are reimbursed for their reports; and diagnoses of autism recorded in the Danish Psychiatric Central Registry. Only specialists in child psychiatry diagnose autism and related conditions.
The study considered the children's s-e-x, weight and gestational age at birth, and age at diagnosis of autism or of a related disorder; the socioeconomic status of the parents; and the mother's education.
The authors found that “There was no increase in the risk of autistic disorder or other autistic-spectrum disorders among vaccinated children as compared with unvaccinated children (adjusted relative risk of autistic disorder, 0.92; 95% confidence interval, 0.68 to 1.24; adjusted relative risk of other autistic-spectrum disorders, 0.83; 95% confidence interval, 0.65 to 1.07).”
In addition, the authors found no association between the development of autistic disorder and the age at vaccination, the interval since vaccination, or the calendar period at the time of vaccination.
Children were vaccinated at 15 to 17 months, and catch up vaccination was given to older children when the vaccine was introduced in 1987. Almost all children were vaccinated before the age of 3 years. The mean age at diagnosis for autism was 4 years, 3 months, and for autistic spectrum disorders 5 years, 3 months.
Although MMR vaccination was introduced in Denmark in 1987, the rise in autism began only in the mid-1990s. “If it [MMR vaccination] caused autism, we would see a greater risk [soon] after its introduction,” Dr Madsen said, but the study did not show that. Autism is increasing, perhaps because of better diagnosis, but there is no link to MMR vaccination, he said.
The retrospective nature of the study may be its strength, Dr Madsen told the BMJ. Recall bias, such as when parents whose children are given a diagnosis of autism recall events that occurred around the time of the diagnosis, was absent. In this study, data on vaccination were recorded separately from data on diagnosis.
MMR vaccination protects children against disease, Dr Madsen said. “Measles kills one in 3000 children, even in developed countries. It causes encephalitis in one in 2000 and pneumonia in one in 20. People tend to forget.”
Wakefield's most widely publicised blunder was the ridiculously small sample-size on which he based his conclusions.
But Wakefiled noted, further, that the children in his study developed, apparently, pretty much normally until the MMR jab was given when shortly afterwards, symptoms of autism began to emerge, from which he concluded that children born without disability were caused to become autistic as a result of the MMR jab.
If only Wakefield had researched the history of work to identify and classify autism, conducted in America shortly after the end of the Second World War, and before MMR was even dreamt of, he would know those researchers noted the exact-same thing. What they concluded from that was something quite different, but equally pernicious and false. They allied that to another observation, true in America at the time they were working, that their client-base was of children born to wealthy and well-educated parents. They noted, further, that the children in their sample made little eye-contact with their parents, a difficulty, actually, in understanding eye-contact, misinterpreted, at the time, as a difficulty in making it, giving rise to the refrigerator mother theory of autism. The theory went that children born without disability were caused to become autistic by their emotionally detached and frigid parents, and especially mothers, who "failed" to make a proper attachment-bonding with their children, resulting in emotional trauma for the child so severe it caused the life-long disability of autism.
In fact, in America at that time, the services that enabled a formal diagnosis of autism to be made were remote, inaccessible and above all, expensive. It was only wealthier and better-educated parents who could, firstly work out how to access these services; secondly, afford to pay for them. Children with autism born to families in the lower scoio-economic groups simply went undiagnosed.
Autism is, and has always been, a disability present from birth whose symptoms become apparent to parents in the later stages of infancy.