A severe mumps outbreak continues to worsen as almost twice as many Aucklanders have caught the illness in the last 10 months as in the two decades prior.
The Auckland Regional Public Health Service says 527 people have now had confirmed or likely cases of mumps in the 10 months to October 5.
By comparison, just 286 people caught the illness - which is spread through the air by breathing, coughing and sneezing - in the 20 years prior from 1997 to January 1, 2017.
"What we have in Auckland right now with mumps is a severe outbreak situation," Medical officer of health Josephine Herman says.
She said the outbreak was hitting Pacific and Māori communities and those aged between 10-and-24 years the hardest.
While about 80 percent of children aged up to 12 are immunised against mumps, Dr Herman says there was now a "lost generation" of young people in their mid-20s, who weren't fully immunised.
This was because of changes made in 2001 to the age at which children were supposed to get their second dose.
National immunisation data also showed only 42 percent of Māori and 45 percent of Pacific children were immunised.
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Mumps can be prevented by a free vaccine available from local doctors.
"We need people to ensure they have had two doses of the measles, mumps, rubella vaccine," Dr Hermann said.
Mumps can cause painful swelling of the gland around the face and jaw, fever and headaches.