Some parents fear MMR causes autism
North Cheshire Health Authority (NCHA) says that coverage with the measles, mumps and rubella vaccine in Widnes, Runcorn and Hale has dropped to only 77%.
This is well below the national average - and about the same level as in Dublin last year when there was a serious measles outbreak.
Public health experts say that anything below 80% over a prolonged period means there is the opportunity for a measles outbreaks to get a foothold in the community as more and more children go unvaccinated.
Measles, in very rare cases, can prove fatal.
Some parents have been reluctant to have their babies immunised due to concerns the vaccine may be linked to autism and bowel disorders, despite a lack of any reliable evidence of this.
Prime minister Tony Blair recently refused to bow to political and media pressure to say whether his youngest son Leo had been given the triple Measles, Mumps and Rubella vaccination.
North Cheshire Health Authority fears the rate will drop further still unless swift action is taken.
It has responded by spearheading a huge publicity campaign.
Strong protection
NCHA's consultant in communicable disease control Dr Bernard Schlecht said: "There is a very real chance of children catching this killer disease this winter if they are not protected with the MMR vaccine.
"Recent media stories have been confusing and caused unnecessary alarm.
"The simple truth is that MMR is extremely safe, safe enough to be used in every country in the world, except Japan.
"I had no hesitation in having my own child vaccinated and I urge all parents to do the same."
After just two doses of the MMR vaccine, 99% of children are fully protected against all three diseases.
The national uptake of the vaccine is currently is 84.6%, which is down from a peak of 92% in 1995.
Measles causes death in up to one in 2,500 cases.
It is also associated with meningitis and encephalitis - inflammation of the brain.
Warnings about the potential for measles outbreaks have already been issued in parts of London where the MMR coverage rate has dropped to similar levels.
Two years ago, an outbreak in Dublin claimed the lives of two children and left hundreds more hospitalised.
Mumps complications include inflammation of the pancreas and damage to the nervous system.
In pregnant women, rubella has a 90% chance of damaging the foetus and babies can be born blind, deaf, with heart problems or brain damage.