AS A homeopath, Peter Adams will not be interested in facts but your readers may be.

In your Letters page November 1, he repeats the usual discredited claims about the harmfulness of vaccines, in particular the MMR vaccine.

He lays the blame for this alleged harm on mercury supposedly contained in vaccines.

The chemical concerned is a preservative called thiomersal, which is indeed a mercury compound.

However it has not been routinely used in UK vaccines since 2005 so his point is invalid.

It was removed not because of any direct health risk but as part of a wider move to reduce environmental heavy metals.

It is still sometimes used in vaccines which need to be mass produced and stockpiled such as those for flu.

It is not present in the MMR vaccine or any other given in childhood.

He should also consider whether autism is in fact increasing.

Certainly the number of diagnoses is increasing but the criteria for making that diagnosis have changed and awareness of the condition has increased.

A number of studies have looked at old medical records where autism was not diagnosed and concluded that on current criteria it would be.

So Mr Adams’ other premise is highly doubtful.

The MMR autism link is still being perpetrated widely so it is worth remembering that it was triggered by a paper in the BMJ by Andrew Wakefield.

Wakefield was subsequently found guilty of fraud and malpractice and was struck off the medical register.

Nonetheless he seems to have found an audience among US conspiracy theorists, including Robert F Kennedy.

Jim Watson