Last February I wrote in this column about autism, and the growing suspicion that it had something to do with vaccinations, particularly MMR. This generated some correspondence, including one letter from the Autism Society saying I had underestimated the incidence of autism, and one from the "proper doctors" saying I had overestimated it, and that vaccines were perfectly safe.

Since then there have been developments. In this country a private GP who was offering single vaccinations (thought by some of us to be safer than the triple vaccine in MMR) was condemned by his local health authority and hauled up before the General Medical Council in less time than the average GP consultation - then cleared of wrongdoing!

But in America things have become more interesting; in May the Institute of Medicine and the National Academy of Sciences -- two of the most prestigious scientific institutions in the USA -- issued a report which was presented in the press as exonerating MMR and vaccinations of any involvement in causing autism. There was an outcry, of course, and in October the IOM released yet another report, this time stating the link from mercury in vaccines to autism was "biologically plausible", and recommending that doctors avoid giving children vaccines with mercury-based preservatives in them, unless alternatives are unavailable. Now why haven't we heard much about that in the news?

We have, though, heard about Tony and Cherie Blair, and as far as I can see every other Cabinet member with children, refusing to say whether they have given their children the MMR jab. To be fair to politicians (something they rarely are with us), if they did insist on waving their children in front of us in this situation we would regard that as distasteful; but the fact that not one of them is prepared to stand up and say 'yes of course my child had the MMR, after all it's perfectly safe' is so surprising that it has to arouse some suspicion.

Does the Government really believe its own hype about this issue? Or have they taken note of the report I mentioned above? Or even of some of the features that have appeared in this paper?

The point about mercury, by the way, is an interesting one. Mercury is a part of the preservative, thiomersal (or thimerosal) used in a range of vaccines - not in MMR, but in almost all the ones given earlier on in life.

When a nurse in America, who is also the mother of an autistic child, realised that in one day of vaccinations her child had several times the officially allowed safe dose, she started a campaign that led to a congressional hearing and the uncovering of the whole story.

Many of the characteristics of autism are similar to those of mercury poisoning - neurological damage, immune effects and so on. Check out www.autism.com/ari and www.cureautismnow.org for the full story.

What seems to happen is that in vulnerable people mercury damage weakens the system so the effect of MMR is more than they can handle, and autism develops.

Not every case of autism develops this way, but most appear to, and experience from working with these children tells us that dealing with the mercury - a long and arduous business - is the single most important thing in healing them.

Thiomersal is now being removed from vaccines in America and Europe so, if the mercury theory is right the rate of autism should start to fall during the next few years.

Getting governments to admit that they were wrong is likely to take somewhat longer.