Imagine that Britain is one large version of Grand Theft Auto. Imagine now that the media is a spotty 14-year-old, gleefully mowing down pedestrians. For almost a decade, from 1997 to 2004, newspapers cheerfully spread the idea that the MMR vaccine caused autism. They trumpeted compelling anecdotes from teary mothers, made fun of those silly science boffins, and sold a lot of papers. It was fun.

In 2004, something that they hadn’t thought of happened: MMR uptake dropped to 80 per cent of two-year-olds from 92 per cent in 1997. Doctors — including one of those who had originally posited the autism link — warned that children could die. The game, it seemed, was interactive. The pedestrians were real and it wasn’t so much fun.

Since 2004, broadly speaking, papers have accepted that they went too far. Stories about MMR are now more likely to rubbish a link with autism. But has it worked?

In 1997, 17 articles in the UK mentioned MMR. In 2004 there were 1,442. If you plot this data against the uptake of MMR, there is a very strong negative correlation (-0.73, for the geeks). This implies that the more the jab is questioned by the media, the fewer people take it. Since 2004, you would expect something different: if more articles support the scientific line, the correlation should move closer towards zero.

What has happened? Well, in the past five years MMR uptake has slightly increased. But there has also been a decrease in the number of articles about it. In fact the correlation between the two is almost unchanged from before (-0.82). This is not good. It doesn’t seem to matter what the articles say — the more there are, the worse it is for MMR uptake.

Last month we learnt that there is a measles outbreak in Wales. The temptation for newspapers is to start writing about MMR again, encouraging vaccination. Perhaps, though, the best thing we can do about it is just shut up.