Archive for February, 2009
(This post was originally posted on the Good Enough Mum blog, here.)
I wanted to write this post because I know that the alleged MMR link has worried many parents, and thought it might help at least some people to hear from a mother and a GP about how and why I reached the decision to give the MMR and why I’m happy with that decision in retrospect. It’s not meant to be an exhaustive study of all the available evidence. It’s the story of the way the evidence looked to me when I was making my own decision about the vaccine, and the factors I took into account. (Obviously, some new and relevant points have come to light since then, all of which have only strengthened my belief that I made the correct decision. I’ve included those as footnotes. The main body of the text is about how I made the decision at the time.)
It is fair to say, first off, that I was quite strongly influenced by what I’d seen of the anti-vaccination movement. Their arguments seemed so loaded with the features I’d learned to associate with poor science (their trumpeting of poor-quality research while ignoring large-scale studies that contradicted their hypotheses, their hints of conspiracy theories, the general impression that they’d made up their minds and now were out to find the data that suited them rather than finding what the data showed and making their minds up based on that) that my automatic inclination was to assume they were wrong. The more anti-MMR hype I saw, the more I found myself feeling that if people who argued that way were against the MMR then I should probably be all for it.
However, in all fairness, I knew that wasn’t really the best way to decide the issue. Just because I didn’t like the way people sounded didn’t mean that I should be dismissing what they had to say out of hand, and the fact that they gave every appearance of jumping to conclusions certainly didn’t mean I was entitled to do the same thing. So I tried to look at the available evidence as fairly as I could. As far as I could see, the story went something like this:
Back in the 1990s, a number of parents had noted that their child seemed to have developed symptoms of autism around the time that said child got the MMR immunisation, and started wondering, worrying, and sometimes drawing conclusions about a possible connection. In 1998, a paediatrician by the name of Andrew Wakefield wrote a paper for the Lancet in which he wrote about twelve children that he’d seen in his outpatients’ clinic with autism and bowel symptoms, eight of whom had allegedly developed symptoms shortly after having the MMR. Wakefield theorised that there might be a link – according to his theory, the MMR might be causing bowel damage which then led on, secondarily, to autism.
So, the question had been raised. However, so far all we had was a question, and it’s crucial to remember that that’s not the same as an answer. Since autism primarily affects areas such as language and imaginative play which undergo noticeable spurts of development during the second year of life, that’s very often when parents first start to notice differences about their child, and since the MMR happens to be given around the beginning of the second year, purely by the law of averages there are going to be a certain number of occasions when parents notice autistic symptoms in their child around the time that the MMR was first given. Not only that, but taking your child to a doctor’s office to have a needle stuck in him is an unusual and nerve-wracking event that tends to stick in people’s memories, so, if your child has autism and you’re desperately wondering what could have caused it and are looking back racking your brain to think what was happening at around the time you first noticed the symptoms of autism, the fact that your child happened to have a vaccine around then is going to be something you’ll remember. It was entirely possible, therefore, that the associations that had been noticed in some children could be purely down to coincidence.1,2 The question had been raised, and it needed an answer.
So – and this was the bit that somehow seemed to get left out of much of the media hype around the topic at the time – researchers set out to find that answer. They looked at large-scale groups of children, looking for any correlation between the age at which children got their MMR shots and the age at which they were first noted to have symptoms of autism that might be above and beyond coincidence, or any link between the sort of bowel symptoms Wakefield had described in the children he’d studied and either autism or the MMR, or – most importantly – any difference in autism rates between children who’d had the MMR and children who hadn’t. Esther, over at Mainstream Parenting, has a good summary of the research in this area, but the important bottom line was that none of these studies showed any link. Children were no more likely to show symptoms of autism just after their MMR than they were at any other time around that sort of age, there didn’t seem to be any sort of link between autism and inflammatory bowel disease, and – most importantly – children who’d never had the MMR were just as likely to be diagnosed with autism as children who’d had it.
The only other arguments in favour of the MMR-autism link seemed to be a claim that there were unexplained rises in the rates of autism in recent years (except that no-one could even say for certain that this was the case, given that this coincided with health professionals becoming a lot more on the ball about picking up subtle symptoms of ASD that might have gone unnoticed before – it looked more as though we were just getting better at diagnosing the cases of ASD that had always been around), and that Wakefield claimed to have found measles virus in the bowel wall of some children with autism (which was supposedly linked in with his whole theory about MMR triggering bowel disorders which then led on to autism, but frankly sounded like a pretty tenuous and inconclusive link to me. Besides, if it turned out that Wakefield was right about that and that measles virus really did put children at risk for bowel disorders, why on earth should that be an argument in favour of me leaving my children unimmunised and thus at risk of contracting the full-strength unexpurgated version of the virus that the vaccine was meant to protect against?)3
And that, as far as I could see, seemed to be evidence in and case closed. We’d questioned whether the MMR might increase autism risks, looked into the matter, found out that it didn’t, and that was that. Since the result of the question being raised in the first place was that a lot of extra research had been done into the vaccine, I felt that – thanks, indirectly, to Wakefield and his cronies – I could feel particularly confident that it was safe to give to my children.
However. I wanted to give the anti-vaccine arguments as open-minded a consideration as I could before rejecting them. Besides, my experience with a health visitor who flat-out refused to accept that Jamie’s near-complete failure to gain any weight in his first two months could possibly have anything to do with his uncut tongue tie had left me with a lot of sympathy for any parent who felt convinced that X had caused Y in their child yet was getting short shrift from medical professionals. So, I played Devil’s Advocate with my conclusion. This is the bit where I feel I’m skating on thin ice, because I know the risk that someone might be disingenuous enough to quote parts of what I’m going to say out of context to support an anti-vaccine argument. I hope people will have the integrity not to do that, and to read the whole of my post and treat it as fairly as I’ve tried to look at the arguments with which I disagreed.
What if, I asked myself, what if there was a grain of truth in the midst of the hype, a flicker of flame in amidst all the smoke? The thing is, no study can prove a negative – that’s just a simple fact of science. No study can ever prove that there is absolutely zero chance of any risk associated with a particular thing or action. So, what if just a few of the parents who believed the MMR had triggered autism actually were right? What if the risk wasn’t actually non-existent, but just so small that all the studies to date had missed it? It would, of course, have to be a pretty miniscule risk for that to be the case; but it remained a theoretical possibility. I felt comfortable with the evidence for the MMR’s safety, but I did also recognise the fact that it was not possible to absolutely completely one hundred per cent exclude any chance of any risk of the MMR causing autism.
This is what I call the ‘Death Rays From Mars’ argument. The name comes from a scene I once saw on a television drama. I have no idea what the drama was or even what most of the plot was, since I wasn’t actually watching it – someone else had the TV on and I happened to be in the room. From what I remember of it, it was a courtroom drama in which a doctor was accused of having caused the death of one of his patients through being unfit to practice. In the scene I remember, the defence lawyer was questioning one of the witnesses, also a doctor, and asked the witness about the possibility that the patient might in fact have died from such-and-such an alternative (and highly unlikely) cause. Was it possible, the lawyer asked the witness, that this whatever-it-was other cause might in fact have been what killed her? The witness fixed him with a weary stare and replied “It’s possible that death rays from Mars killed her.”
The moral being, of course, that just because something’s possible in the can’t-one-hundred-per-cent-disprove-it sense doesn’t mean that it’s a possibility we actually have to take seriously for practical purposes. But also that the whole ‘but it’s possible that…’ argument can get very silly. If we’re going to worry about the possibility that something might happen even in the absence of any evidence that it will and/or the presence of positive evidence that it won’t, then where do we stop?
So, my answer to the idea that, theoretically, there might still be an infinitesmal risk of the MMR causing autism was “Compared to what?” If you’re going to start worrying about hypothetical undetectably small risks of the MMR causing autism, why stop there? The whole point about vaccines, after all, is that they’re given in order to stop a child contracting the actual diseases. It’s every bit as logical to hypothesise that infection with measles or mumps or rubella themselves might carry that risk. It seems to me to be rather more illogical to claim that the weakened viruses in the injection are too risky to give to a child but that it’s quite all right to leave that same child unprotected against the full-strength viruses that they might then catch. At least the possibility has been thoroughly studied in the case of the MMR vaccine – I don’t know of any study reassuring me that children aren’t at any increased risk of developing autism as a result of catching rubella.
But I did, on the other hand, know of incontrovertible evidence of problems and risks that are associated with catching measles or mumps or rubella. Fatalities and serious complications from measles or mumps may be rare in healthy children, but they do happen. Rubella wasn’t something that would cause Jamie himself any problems, but what if he caught the disease and passed it on to a pregnant woman? A decision on my part not to immunise my own healthy child could indirectly have devastating lifelong consequences for another child. And, of course, if Katie wasn’t immunised against rubella she ran the risk of having a severely damaged child herself – an actual, known, proved risk, unlike the theoretical in-the-face-of-all-the-evidence risk that the MMR supposedly carried.
Even an uncomplicated case of these diseases can be pretty darned unpleasant experience for the child. My sister had measles as a child – no complications, no problems, just a straightforward case with a straightforward recovery. Over twenty years later, I can still remember how miserable she was with that particular ‘simple childhood illness’. I didn’t find it at all difficult to decide that I’d like my children to be spared that experience.
So, there you have it. My decision wasn’t based on a belief that there’s absolutely no chance that the MMR could possibly have caused autism in any child ever ever ever. It was based on a belief that, between a theoretical possibility of an MMR risk too small to show up on any studies and a theoretical possibility of a completely unstudied and unquantified autism risk with measles or mumps or rubella, on top of the actual known side-effects of those diseases, I found it a no-brainer to go for the option that had been most extensively studied and had repeatedly come up in the studies as showing no problems. In other words, the MMR.
1. One other factor here is the possibility that, once a few people have voiced their concerns about the MMR and thus started other people wondering, this in itself can make people more likely to conclude that their child’s disorder may have been caused by the MMR, and that can affect the way in which people remember and interpret events. There is now evidence that at least some of the children who are believed by their parents to have developed autism only after the MMR actually had documented evidence of autistic features and/or of concerns about their development before having the MMR, Michelle Cedillo being the most famous such case.
2. With regard to Wakefield’s paper, it has now turned out that it was indeed not a coincidence that several of the parents whose children came to see him reported their child showing symptoms of autism after the MMR. However, the link wasn’t due to the MMR having caused autism. It was due to the fact that Wakefield had previously expressed sympathy with the belief in an MMR-autism link, and thus lawyers representing families with this belief in planned court cases against the vaccine manufacturers were deliberately advising them to go to Wakefield to get their children seen by him. Wakefield knew this perfectly well but didn’t report it in the paper he wrote, despite the fact that it would have put an important new slant on others’ interpretation of the results to know that all these children hadn’t shown up in one hospital’s outpatient clinic through sheer random chance. He also didn’t report the payments he was receiving from the lawyers for this work, even though it’s considered ethically correct for the author of a medical paper to report all conflicts of interest at the end of the paper.
3. Wakefield’s laboratory experiments in this area have since been completely discredited, as it has been shown that his work was riddled with errors in technique that could have caused false positive results. The same studies have been attempted by other researchers using correct techniques, and no-one else has found any sign of measles virus in the guts of autistic children.