Good news! The Lancet has retracted Dr Andrew Wakefield’s paper linking the MMR (measles, mumps and rubella) vaccine with autism and bowel disorders. This is not before time; the damage done by this particular paper in a journal as respected as The Lancet has been enourmous. The journal has admitted that it should never have published the flawed research in the first place, which implies that in this case there was a failure of the peer-review process and that steps should be taken to avoid a repetition of that failure.
The retraction of the paper was not a spontaneous decision to do the right thing on the part of The Lancet, however. It came in response to an editorial in the rival British Medical Journal that was to have been published today calling for its retraction. One hopes that The Lancet will be more careful in future.
The vaccine-autism debate has raised a lot of issues that now need to be ingested, digested, mulled over and taken into the public conciousness. As with all scientific subjects that become politicised, this one has raised questions about the quality of scientific journalism, the lack of science education and the inability of the public to understand, even in the most superficial way, the scientific process.
Firstly, there is a profound misunderstanding of the very nature of science. The man in the street seems to be under the misapprehension that science consists of “proving” things. We only need one exception to disprove a rule, but in order to prove a rule we must prove it for every case, which is usually impossible to do. So when a paper appears in a medical journal statistically linking autism with vaccines, newspapers immediately run headlines like “VACCINES CAUSE AUTISM, STUDY SHOWS”, even if the original paper made no such claim. The fact is that science very rarely proves anything—that is the sphere of mathematics. Science can only pile up evidence in the form of data that may or may not support a particular hypothesis. In this case almost all the non-fabricated evidence did not support the hypothesis that vaccines cause autism.
So why the statistical link? Well, there are other explanations than that vaccines cause autism. The age at which the diagnosis of autism can be made is about the same age as the MMR vaccine is administered. A parent who has his child vaccinated and then the child is diagnosed as autistic a few weeks or months later may be forgiven for thinking that the latter may be caused by the former. But, as we all should know, correlation does not necessarily imply causation.
Why has the incidence of autism been increasing as vaccination has become more widespread? Again, there are other factors that may be at work. The diagnostic criteria for autism have changed: a child who may, a few decades ago, have been regarded as merely shy may today be diagnosed as autistic. The anti-vaccination factions originally blamed Thimeresol (which was used a preservative in the vaccine) for causing autism. Thimeresol was duly removed wihout having any affect on the incidence of autism, strong evidence that it was not a cause of autism.
There is strong psychological need for people to aportion blame for any misfortune that may befall them, so parents grasped at the vaccine explanation as a drowning sailor would clutch upon a passing liferaft. I sympathise with such parents, but their actions have consequences among the wider community. Once a sufficient proportion of the population are vaccinated against a particular disease, the pathogen can no longer be propagated and the population as a whole develops “herd immunity”, even those who for other reasons (allergies, for example) cannot be vaccinated. When parents decide not to vaccinate their children they put herd immunity in jeopardy, which places all unvaccinated children at risk, not just their own.
Will The Lancet’s decision have any effect on the anti-vaccination lobby? Probably not for the die-hards—their minds are incapable of change. It will have an effect on the medical fraternity, though, and those doctors who are advising their patients not to vaccinate their children may undergo a change of heart. We can only hope that the anti-vaccination lobby becomes a part of the lunatic fringe like the moon-landing-hoax crowd: not taken seriously by anyone with any vestige of sanity.
Grumpy Old Man by Mark Widdicombe is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 2.5 License.