There have been more than 1,000 measles cases so far this year – putting Britain at risk of a deadly epidemic, health officials say.
The Health Protection Agency blamed unfounded fears about the combined MMR jab for the increase and urged parents to vaccinate their children.
In the first ten months of 2008, there were 1,049 confirmed cases in England and Wales – the highest level since the early 1990s.
A recent outbreak of more than 60 cases in Cheshire has prompted the launch of a programme to vaccinate 10,000 pupils.
The agency blamed the rise on a low uptake of the MMR jab over the past decade.
A panic among parents was triggered by researchers who claimed there was a link between the combined measles, mumps and rubella jab and autism. Most experts believe the jab is safe and effective.
Around three million children and teenagers are believed to be at risk of a measles epidemic because they missed one of two doses of vaccine, or are entirely unprotected.
The disease can lead to ear infections, pneumonia, and permanent brain damage, and may even be fatal.
HPA immunisation expert Dr Mary Ramsay said: 'Over the last few years, we have seen an unprecedented increase in measles cases and we are still receiving reports of cases across the country.
'This rise is due to relatively low MMR vaccine uptake over the past decade and there are now a large number of children who are not fully vaccinated with MMR.
'There is now a real risk of a measles epidemic. These children are susceptible to not only measles but to mumps and rubella as well.'
The NHS information centre said uptake rates of the triple jab remained at 85 per cent in 2007-2008, the same as the previous year. A rate of 95 per cent is needed for immunity in the community.
In August, the Chief Medical Officer announced an MMR catch-up programme to reduce the risk of a measles epidemic.
Primary Care Trusts and GPs were urged to identify individuals not up to date with their MMR injections and offer catch-up immunisation
The move was based on models of measles transmission in England carried out by the Agency, which suggested there was a real risk of a large measles outbreak of between approximately 30,000 to 100,000 cases - with the majority in London.
Dr Ramsay said: 'We are glad to see that public confidence in the MMR vaccine is now high, with more than eight out of 10 children receiving one dose of MMR by their second birthday.
'But we shouldn't forget that the children who weren't vaccinated many years ago are at real risk.
'Measles is a very serious infection as it can lead to pneumonia and encephalitis, even in healthy children. It is highly infectious - it can be passed on without direct contact before the rash appears.
'This is why it's incredibly important to continue to remind parents about the benefits of having their child vaccinated with two doses of MMR for optimum protection. It is never too late to get vaccinated.'
A mass vaccination is to take place in Cheshire in early December.
The parents of 10,000 children have been asked to give consent for the MMR vaccine after tests confirmed 19 cases in the region, with a further 49 youngsters being treated for 'probable' measles.
Most reported cases were in Sandbach, Middlewich and Crewe, but there have also been reports from Congleton, Nantwich and Winsford, Central and Eastern Cheshire Primary Care Trust said.
Guy Hayhurst, consultant in public health at the trust, said: 'We identified 10,534 children who had no record of full MMR immunisation and wrote to their parents to seek consent for them to be vaccinated in school.
'We hope that by doing this we will halt the current outbreak in its tracks, or at least severely curtail it.'
Teams of nurses are being prepared to vaccinate children in 177 primary schools and 33 secondary schools. The vaccine will also be offered to younger school staff members.
The mass vaccination programme will begin on December 3 and is expected to be completed by December 17.