Parents were last night urged to get their children immunised after it emerged that more than 11,000 children across Norfolk, Suffolk and Cambridgeshire have not been vaccinated against measles.

The head of public health in Norfolk warned that nothing was stopping a major outbreak in the region because not enough people had received the MMR jab.

A national catch-up programme to increase vaccination uptake in children and teenagers has been launched to prevent the spread of the contagious disease, which has resulted in more than 500 cases across England this year, with 100 people hospitalised.

More than 1,000 cases have been reported in the Swansea area of Wales.

Public health officials have now called on parents to get their children protected after it emerged that an estimated 7,924 10 to 16-year-olds in Norfolk and Suffolk had not received the MMR vaccine to protect them against measles, mumps and rubella. A further 9,818 children across the two counties are not fully protected after only receiving one of the two MMR jabs recommended, leaving around 10pc of children at risk of getting measles, according to figures from the Department of Health. In Cambridgeshire, there are 3,788 unvaccinated 16 to 10-year-olds and a further 3,011 with partial protection.

Lucy Macleod, joint interim director of public health at Norfolk County Council, said there had been three measles cases in the first three months of 2013 in Norfolk: but there was nothing stopping a major outbreak locally.

'The message is that there is no need to panic, but on the horizon there is the possibility of an outbreak. There is nothing unusual about Norfolk and there is just as much risk in Norfolk. We do not have the right level of immunity in the population to step down on an outbreak if we had one. We want to raise the level of immunity so it will not take hold.'

'We need to get the immunisation rate up to 95pc, which is needed to stop regular outbreaks,' she said.

Public health officials are sending out fact packs to local children's centres and pre-schools urging them to vaccinate their children.

Mrs Macleod added: 'Our role is to make sure the message gets out there and have an overview of the statistics and to raise questions if there are areas where it is not particularly great. We do get outbreaks of mumps, but measles is particularly a concern and was almost eradicated 25 years ago and it really can be a serious disease and can cause fatality. It is classed as a mild disease, but it is not and it is essential that children are vaccinated.'

The first MMR vaccine is to babies as part of their routine vaccination schedule, usually within a month of their first birthday, with the second injection before starting school.

In 2011/12, 84.7pc of children had been immunised by their fifth birthday in Norfolk and 85pc of children in Great Yarmouth and Waveney, with the national figure at 86pc.

The number of unvaccinated children has been blamed on the publication of a widely discredited and unfounded report by former surgeon and researcher Andrew Wakefield in 1998, who raised the possibility that the MMR jab might be linked to autism and bowel disease.

The highest number of measles cases in England have so far been in the North West and North East.

Dr Gina Radford, director of the Anglia and Essex Public Health England Centre, said: 'The catch-up programme recommends an approach to specifically target those young people most at risk, particularly the 10-16-year-old age group. We would advise those who have not been vaccinated to seek at least one dose of MMR vaccination which will give them 95pc protection against measles. A second dose is then needed to provide almost complete protection.'

'The only way to prevent measles outbreaks is to ensure good uptake of the MMR across all age groups, and that when cases are reported, immediate public health action is taken to protect vulnerable individuals as soon as possible.'

'It is never too late to get vaccinated against measles. We would urge parents of unvaccinated children, teenagers and young adults who have missed out on MMR to arrange to be vaccinated by their GP. If you are unsure whether you or your child has had two doses of the vaccine, speak to your GP who will have a record.'