A rise in the cases of mumps in the east of England has prompted a primary care trust to offer vaccinations to pupils at four state schools.
School nurses will be visiting schools to give the jab
Uttlesford Primary Care Trust in Essex has written to parents with children aged 14 to 18 to offer the jab.
Health workers say that of the 1,600 students who need to be vaccinated, about 200 have never had the MMR vaccine and 1,400 will need a booster.
School nurses will visit the secondary schools over the next few months.
Sue Moss, from the trust, said: "We need to dispel the myth that mumps is an illness you get as a child.
"Mumps can be caught at any time in your life and the older you get, the more unpleasant it is."
There were 12 cases of mumps in the eastern region in 2002.
This year that figure has increased to 2,088 so far in 2005 - the highest numbers are in the 15 to 19 age group.
Health officials say this group is at greater risk because they would only have had one MMR jab as children, whereas toddlers now have two.