The MMR vaccine was launched in America in 1975, Scandinavia in the early 1980s and Britain in 1988. The jab is now used in more than 30 European countries, as well as Canada, Australia and New Zealand.

The biggest-ever study of the MMR vaccine tracked the effects on 1.8 million children vaccinated in Finland between 1982 and 1996. Three million doses were followed up by researchers, who could not link them to a single case of autism.

One MMR vaccine is currently available – a further two brands were withdrawn from the British market in 1992 as the mumps section of the jabs had been linked with mild meningitis.

One measles case in every 100,000 causes brain illness and death. Mumps can lead to sterility in adult males, and rubella in early pregnancy can cause birth defects in babies.

The MMR vaccine can prevent measles infection in 90 per cent of all immunised children. A second dose raises this to 99 per cent.

The first dose of vaccine is normally given by a GP at between 12 and 15 months. The booster is given at between three and five years.

In Ireland last year a drop in take-up of MMR vaccine led to a measles outbreak in Dublin, killing two children and harming others.

In France, MMR coverage is still only 85 per cent, despite vaccination being compulsory before a child can attend school.

Around 95 per cent of children have to be vaccinated, but autism fears have reduced uptake to less than 80 per cent in most British cities. Two million youngsters in Britain are given the jab every year.