In February 1998, the medical journal The Lancet published a clinical report written by Dr Andrew Wakefield and 12 other medical research scientists.

From that report, a great debate about a possible link between MMR and autism has sprung. What I want to do in this post is to summarise the issues as briefly and as well as I can, in as objective a way as I can – something I have not yet seen anywhere I have looked, in this area which seems to generate so much heat and strength of feeling.

(Please note: I have not read the Lancet article itself – the Lancet limits access to that article to its subscribers and I have decided against paying £120 to subscribe! – so I paraphrase from what I have read about the article and am glad to be corrected if my account is inaccurate.)

The report detailed a study of 12 autistic children suffering from bowel disease. Parents of eight of the children reported that symptoms began after the MMR vaccine and parents of one child said that symptoms began after a bout of measles. Measles viruses were found in the diseased bowel tissue of those nine children.

Wakefield’s idea, shared by his co-authors, was that the bowel disease suffered by these 12 children could be linked to their autism. Autism is not normally associated with bowel disease, however it was suggested that these children had a particular type of autism, which was said to be novel (i.e. previously unrecognised) and which was linked to or caused by the bowel disease.

The report then suggested that the bowel disease might have been caused by measles virus, perhaps from the MMR vaccine, and hence that MMR might have caused their autism.

(Wakefield had already suggested a link between measles and/or the measles vaccine and Crohn’s disease, a bowel disease – a link which no studies have been able to confirm.)

The report stressed that no link had been proved but that further investigation into this possibility was merited. Wakefield went further, and suggested in a press release that the triple MMR vaccination should be replaced with single vaccines at least a year apart pending further study into the safety of MMR.

Over the next six years, public debate raged.

Wakefield’s integrity was questioned, since he was working both on this study and, at the same time, on a study funded by the Legal Aid Board for the purpose of providing evidence as to whether MMR might have caused autism in children whose families wished to take legal action against the vaccine manufacturers. It was said that this amounted to an undisclosed conflict of interest, throwing doubt upon the objectivity of the report. The facts relating to the 12 subject children were not disputed, but the interpretation placed on those facts was said to have been (potentially) influenced by work on this other project. The suggestion by Wakefield that MMR be dropped pending further studies was widely considered to be a highly irresponsible and ill-avised remark that grossly exaggerated the strength of the evidence in the report.

Meanwhile, publicity surrounding the report triggered a massive drop in the uptake of MMR. Public concern about this vaccine, and public mistrust of the health authorities who promoted its use, combined so that many parents chose to leave their children unvaccinated or to take up single vaccines instead. This was described by many as a public health crisis.

Under considerable pressure, then, a partial retraction of the original report was orchestrated. In February 2004, 10 of the 13 authors signed up to a statement that retracted not the facts stated in the report but the interpretation placed upon them. It was accepted that there was no credible evidence of a link between MMR and autism. Wakefield refused to sign up to any retraction, saying that it was always clear that no link had been proved but confirming his view that more research was needed in order to confirm or rule out such a link.

What further research has there been?

Many epidemiological studies have been conducted. These studies take large populations and use statistical techniques to identify factors that might be associated with increased risk. They all showed that children who have had MMR are at no greater risk of becoming autistic. They showed that children who are autistic are no more likely to have had MMR. They compared statistics to see if there was any association in time between MMR and the onset of autims and found that there was not i.e. MMR does not trigger autism in children who would later have bcome autistic in any event. They therefore show that, at least as far as these studies can go, there is no reason to believe that there is a link between autism and MMR.

That is not, quite, the end of the matter. It is possible that a small number of children, who are perhaps genetically susceptible, may develop a particular kind of autism as a very rare reaction to MMR. If this is the case, it is altogether possible that the number of children affected is so small that they would not be expected to show up on epidemiological studies. A link between MMR and autism in these children – if there is such a link – could only be established by clinical examination of affected children to find evidence of that link. However so far, despite the best efforts of Wakefield and others – no such studies have found any credible evidence of a link.

The matter is by no means closed, because there are still those out there trying to find out if there is really a link. But the best answer that we can get based on the evidence we have right now is that there is almost certainly no link. And, if there is a link, it is one that is only relevant in a very small number of cases so that the risk (if there is one) is extremely low.

In short – I’m glad that the scientists will keep working on this but, in the meantime, I do not believe that there is any rational basis for a wider public concern about MMR causing autism.