The Ministry of Health has written to school principals advising them to ensure all pupils, parents and staff are immunised against measles as an outbreak threatens to sweep the country.
One senior medical officer is also warning New Zealanders aged between 17 and 23 are at risk because of a change in vaccinations 13 years ago.
The letter has gone to every school and preschool in the country in a bid to stem the contagious disease.
There have been 79 confirmed cases of measles since December - 59 in Auckland, 15 in Bay of Plenty, three in Wellington and two in Hawke's Bay. More than half of Auckland's cases are senior pupils at Westlake Boys High School.
Director of public health, Dr Darren Hunt, has asked schools to update registers to readily identify any unimmunised children in contact with measles.