Urgent proactive action is needed to protect young people from the worst mumps outbreak in a decade, health experts warn.

The outbreak started in Auckland early last year and was initially focused on five schools in the west of the city. Since then there have been more than 1000 cases with some spreading to other centres around the country.

Urgent proactive action is needed to protect young people from the current mumps outbreak in New Zealand, Dr Ayesha Verrall, an infectious diseases physician and researcher at the University of Otago, said.

"Young adults in high-risk settings can benefit from a third dose of the Measles Mumps and Rubella (MMR) vaccine, even if they completed their two doses as a child," Verrall said.

"The vaccine is about 90 per cent effective against mumps, but its protection reduces over time so young adults who received two doses might have lost their protection from the vaccine."

Overseas studies have shown that giving a third dose makes university students much less likely to get mumps than those who only had the two childhood doses.

"Failing to address this fact limits our ability to respond to control the outbreak, meaning mumps will disrupt education, sports and community activities for young people for the next several years," Verrall said.

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Verrall said the Ministry of Health needed to urgently fund and offer a third dose to these people aged 10 to 29, even if they already have had two doses.

In December 2017, 11 months after the start of the outbreak, the Ministry of Health announced a school-based "catch up" campaign for those who did not complete two doses in childhood but concrete plans are not yet in place.

"New Zealand needed to start a catch-up vaccination campaign for adolescents and young adults five years ago if we were serious about preventing this outbreak. But starting one during this historically large outbreak will have limited benefit," Verrall said.