Dr Mary Ramsay warned that vaccination was vital

The vaccine has been given the all-clear by the Department of Health, and new US research published this week also suggests MMR is safe.

But continued concern has led to immunisation rates falling dangerously low in some parts of the UK.

This fall is not the cause of an upsurge in mumps cases - but it could further exacerbate the problem in future.

Children at risk

Most of the current rise in cases has been recorded among children who were too old to receive the combined MMR vaccine, which was introduced in 1988, or among those who have only had one of the two jabs needed to give full protection.

The increase in cases is not a result in the decline of MMR uptake; however, it does illustrate clearly why it is so important that children are given good protection against all three diseases

Mary Ramsay, PHLS

Dr Mary Ramsay, PHLS consultant in public health medicine told BBC News Online that children aged 12 to 18, who were toddlers before the MMR was introduced, were ones who had just missed out.

They would have received single measles vaccine, or a combined measles and rubella jab, though very few would have received a mumps vaccine.

Some were offered a shot of MMR when they first went to school as part of a catch-up campaign in 1994.

However, they did not receive the second jab needed to provide secure immunity.

Dr Ramsay said: "The increase in cases is therefore not a result in the decline of MMR uptake; however, it does illustrate clearly why it is so important that children are given good protection against all three diseases.

"MMR vaccine gives children good protection against measles, mumps and rubella all in one go; by separating the vaccines, we leave children unprotected against some of the diseases, and risk an upsurge in the cases of infection."

Black spots

Stockport is the latest place to be hit by an increase in the incidence of mumps. with 50 cases reported since Christmas. Bradford has also been hit, with 288 cases reported between April 2000 and March 2001, compared to 15 the previous year.

Complication rates

Viral meningitis - 3 in 100 Brain inflammation- 1 in 6,000 1/4 to 1/2 of brain inflammations lead to one or two-sided deafness

Dr David Baxter, consultant in communicable diseases for Stockport Healthcare NHS Trust told the BBC three in 100 cases of mumps could lead to viral meningitis and one in 6,000 could lead to encephalitis, a swelling of the brain. Of those, between a quarter and a half could lead to one or two-sided deafness.

He added: "The cases started to appear just before Christmas.

"We checked their immunisation history and in many of them we found they had had just one MMR."

"This has got grave implications, given the rising problems with MMR.

"If parents aren't taking up the MMR and 12% aren't - and if they're not giving the second MMR, we will soon see the emergence of measles, mumps and rubella - not just mumps."<

Two schools in the town have been particularly hit by cases. There have been 20 at Bramhall High School and six at nearby Ladybrook Primary School. Parents have been warned to be on the look-out for symptoms.

The most recognised symptom of mumps is a swelling of the lymph nodes on the side of the neck, which can make patient's faces look round and swollen.

However, the virus can also cause fever, headaches and muscle aches.

In a minority of cases it can also lead to meningitis, inflammation of the testicles, ovaries or pancreas and deafness.