AN epidemic of measles, mumps and rubella may hit Huddersfield this winter.
Doctors fear a huge drop in the number of children receiving the controversial MMR vaccine could pose serious health problems.
Dr Sohail Bhatti, public health director for Huddersfield, revealed that the town's population is no longer protected from the diseases.
This has been caused by a 20% drop in the vaccination rates of children against measles, mumps and rubella (German measles).
Dr Bhatti said: "There is a very real danger of these diseases returning to modern society if effective levels of immunity are not re-established.
"We need to take urgent action to raise awareness of the devastating effects of these illnesses and encourage parents to have their children vaccinated."
The latest uptake figures from March, 2003, show the number of children up to the age of nine of age who have had their MMR vaccination in the town has been about 30,000.
But more than 6,000 have not had the vaccinations.
The worst problems are in the area covered by Huddersfield Central Primary Care Trust (PCT), in and around the town centre and the surrounding districts.
There the uptake rate is 76.3% - and experts believe a rate of 95% is needed to be effective in eliminating the risk of an epidemic.
In the area covered by South Huddersfield PCT the uptake figure is 88.6%.
Uptake of the MMR vaccine across Huddersfield five years ago was roughly in the mid-90s.
Dr Bhatti said: "Because these diseases have become rare through the previously effective immunisation programme, many people don't realise that they can lead to some serious complications."
Mumps can cause reduced fertility and miscarriage and, very rarely, also inflammation of the central nervous system.
Complications of measles can include ear infections, convulsions, pneumonia, conjunctivitis and, occasionally, more serious eye problems. The heart and nervous system may also be affected.
Measles can be fatal or lead to continuing disability. Prevention is the best option, as no cure yet exists.
Rubella is a mild viral illness, but if a woman catches it in early pregnancy it can have serious effects on the unborn baby and termination is often recommended.
Numbers of vaccinations have dropped nationally since two scientists in London claimed they had found a link between the MMR vaccination and autism. One recently denied a link.