More than a million schoolchildren could be susceptible to measles due to the MMR vaccine scare, warn child health doctors in the UK.

They say a generation of unprotected children are now in secondary school, where they are at greater risk.

Dr David Elliman, from the Royal College of Paediatrics and Child Health, said he was "surprised" outbreaks had not been more common.

A large epidemic centred on Swansea has now affected 808 people.

In response, MMR jabs are being offered in schools in parts of mid and south Wales. Dr Elliman said there was a real danger of outbreaks in other areas and the cases in Wales must act as a warning.

Vulnerable

Measles is a highly contagious disease characterised by a high fever and a rash. In one in 15 cases it can lead to severe complications such as pneumonia and inflammation of the brain.

Two doses of the MMR jab gives near complete protection against the infection.

Uptake is now as high as ever with more than 91% of children under the age of two getting the first dose of the jab in England.

But a decade ago many parents refused to have their children vaccinated after Andrew Wakefield's now discredited claims of a link between the jab and autism.

The precise number of children with no protection against measles is uncertain, but health professionals say it is at least a million children and may be significantly higher.

Dr Elliman told the BBC: "These children are now 11 or 12-years-old, they weren't immunised at the time and their parents haven't caught up.

Children are going to get measles - there is no question Dr Helen Bedford, UCL Institute of Child Health

"They are now starting secondary school so they are vulnerable, they are mixing with large numbers of children, so collectively there is a large group who are unimmunised.

"We would be very worried that that's the group we're going to see outbreaks in."

Growing danger

Cases have been increasing.

Across the whole of England and Wales there were 2,030 cases last year - the highest figure in nearly two decades.

The health secretary, Jeremy Hunt, has already urged parents to get their children vaccinated.

Dr Helen Bedford, from the UCL Institute of Child Health, said there had been outbreaks across the country and further epidemics could be expected.

"Children are going to get measles, there is no question, because there is a great big group - probably of the order of approaching two million children - who are susceptible who have not been immunised."

She said London was a particular problem as in some areas the vaccination rate fell to 50% at the height of the MMR scare 10 years ago.

The government's chief scientific adviser, Sir Mark Walport, told the BBC that parents should vaccinate their children.

"It is an example of how people forget the danger of diseases such as measles.

"They become complacent when it appears to have disappeared.

"But it's just, I think, very clear evidence of the huge importance of vaccination.

"It was and has been one of the major interventions in public health and its absolutely vital that people vaccinate their children."