The MMR jab protects against measles, mumps and rubella
Cases of mumps in Greater Manchester are eight times higher than they were a year ago, according to officials.
The Health Protection Agency (HPA) is urging parents to ensure children are vaccinated after 34 confirmed cases since the start of 2009.
The figure will rise if any more of the current 223 "notified" cases are confirmed by lab testing.
There were just four confirmed cases in the same period last year, out of 68 notifications, the HPA said.
Across north-West England last year there were 287 confirmed cases of mumps, compared to 159 in 2007.
Mumps cannot be treated and can lead to complications including viral meningitis and hearing.
Older children vulnerable
Many children now in their teens missed out on the MMR vaccine after now discredited research linked it to autism.
Dr Rosemary McCann, the HPA's regional immunisation lead, said: "Every child should receive two doses of MMR vaccine, one at 13 to 15 months and a second before starting school.
"Parents are increasingly recognising the importance of having their children vaccinated at the recommended age and uptake rates are increasing.
"But we have a large pool of older children and teenagers who are not protected.
"In 2009, we are continuing to see a sharp rise in mumps cases compared to last year."
Most of the cases are young people aged over 15, with many at colleges and universities.
"Our message to these older unprotected children is that it is not too late," Dr McCann said.
"Anyone up to the age of 18 is entitled to vaccination on the NHS. Parents of children who are not protected can arrange vaccination through their family doctor."