More cases of mumps have been reported this year in Auckland than in the past 16 years combined.
The Auckland Regional Public Health Service had been notified of 300 cases of mumps from January 1 to September 4 this year.
"Mumps is now at large in the community and the only way we can stop this spreading further is to achieve high levels of MMR vaccination in the population," Medical Officer of Health Dr Josephine Herman said.
She said the large number of mumps cases meant a large number of people were also at risk of contracting measles and rubella.
"The implications for young adults are deeply concerning, given the risk of non-immune pregnant women catching rubella. This can result in miscarriage or still birth and babies developing severe birth defects," Herman said.
Mumps also posed a risk of miscarriage for women who were in their first three months of pregnancy, and in rare cases could cause male sterility.
She said there was a "lost generation" where many young people between 10 and 29 had not been vaccinated.
That was partly due to the now discredited MMR controversy from 1998 onwards and a pool of adults who may have missed out on receiving the second dose of the MMR vaccine when they were children when the timing of this dose was moved from 11 years to 4 years in 2001.
Herman said measles was an additional threat to communities with low vaccination coverage.
"It is likely we'll see further measles outbreaks in schools similar to those in 2011, 2014 and 2016. The measles virus is highly contagious and can lead to serious medical complications as well," Herman said.
Parents who were unsure about their family's MMR vaccinations were being urged to check with their practice nurse or look up their children's blue Well Child book.
According to national immunisation data, the coverage rates in young children up to the age of 12 years were about 80 per cent.
Today's mid 20-year-olds had even lower rates, with a national coverage survey reporting that only 60 per cent of Pakeha children were fully immunised in 1991, with lower rates for Maori (42 per cent) and Pacific children (45 per cent).