Measles cases have soared, it emerged today.
There have been 1,049 cases confirmed in England and Wales up to the end of October, surpassing last year's total of 990.
Health chiefs said it was because of the relatively low take-up of the combined measles, mumps and rubella jab over the last decade.
This was triggered by now-discredited research claiming there was a link between the jab and autism.
Dr Mary Ramsay, an immunisation expert at the Health Protection Agency, 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.
"One thousand and forty-nine is the highest number of measles cases recorded in England and Wales since the current method of monitoring the disease was introduced in 1995.
"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. This means that measles is spreading easily among unvaccinated children.
"There is now a real risk of a large measles epidemic. These children are susceptible to not only measles but to mumps and rubella as well."
In August, the Chief Medical Officer announced an MMR catch-up programme, which urged Primary Care Trusts and GPs to identify individuals not up to date with their MMR and offer catch-up immunisation to reduce the risk of a measles epidemic.
The move was based on recent modelling research carried out by the Agency, examining the potential for measles transmission in England, which suggested that there was now a real risk of a large measles outbreak of between approximately 30,000 to 100,000 cases - 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.
The parents of 10,000 children have been asked to give consent for the MMR vaccine after tests confirmed 19 cases, with a further 49 youngsters being treated for "probable" measles.
Most of the reported cases are 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 17 December.
The breakdown of this year's cases nationally is: North West - 106; North East - 9; South East - 76; South West - 29; East of England - 62; East Midlands - 23; West Midlands - 40; Yorkshire and Humberside - 45; London - 626; Wales - 32; Unknown region - 1.Reuse content