One million schoolchildren in England who missed MMR jabs are to be targeted by a vaccination plan aimed at curbing the growing threat of measles.
Health officials warn epidemics similar to the one in Swansea, which has seen nearly 900 cases, could occur anywhere.
There are fears that a generation of children have low levels of protection after the MMR scare a decade ago.
The catch-up campaign, run through GPs, schools and community groups, will focus on children aged 10 to 16.
The campaign is expected to cost £20m and the Department of Health already has 1.2 million vaccines ready to go.
It will aim to vaccinate children yet to be protected with the MMR - measles, mumps and rubella - jab by September.
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, and can be fatal.
In 2012, there were nearly 2,000 cases of measles in England - the highest figure for nearly two decades. This year could be another record with cases already higher than at the same point last year.
Discredited claims by Andrew Wakefield of a link between MMR and autism led to vaccination rates falling to 80VIRTUAL-SkimlinksPromo%