Te Whatu Ora Health New Zealand is urging students and staff at Auckland's Albany Senior High School to "stay away" following a confirmed measles case.
In a statement, a Te Whatu Ora spokesperson said a student attended school while infectious with measles on Thursday, April 27 and Friday, April 28.
"All household contacts are currently in quarantine," the spokesperson said.
Public health staff are working to identify close contacts of the measles case.
"Public health is asking all staff and students to check their immunity and stay home in quarantine if they are not immune. People are considered immune if they have evidence of two Measles, Mumps and Rubella (MMR) doses after 12 months of age, having had measles or were born before 1969. Staff and students will be contacted by Public Health."
Te Whatu Ora said the school is already closed for teachers only day on Thursday, however, information has been sent to the school community alerting them to the additional closure on Friday.
National public health service interim clinical lead Dr William Rainger said while many students will be fully vaccinated, public health staff need to close the school to review the immunity of the 100 staff and 900 students.
"Public health is working as quickly as possible to check immunisation records, and will be in touch with students who are not immune to ask them to remain in quarantine and to provide them with further advice and support."
Dr Rainger is asking staff and students who don't have two MMR vaccinations to stay home and not go to work, social or sports events, or have visitors.
"The quarantine period for non-immune close contacts starts on Thursday (4 May) and they are required to stay away from others in case they are developing measles for a further seven days."
Dr Rainger said Albany Senior High School is a "modern learning environment" and the infectious students spent time in five open-plan halls while infectious.
There is mixing with a number of year levels and classes, he said.
"As a result, around 100 staff and 900 students are considered contacts and we need to confirm their immunity."
The Auckland Regional Public Health Service has forced the school to close under the Health Act.
Public Health is investigating the source of the infection, and Te Whatu Ora said the case has not been overseas recently. This means they were infected by someone with measles within New Zealand, they said.
They added the source of infection is likely to be a person known to the student who has recently travelled.
"Measles is a highly infectious illness and can make people very unwell. It spreads very easily amongst people who have not had measles before, or who have not been immunised."
Te Whatu Ora is urging anyone with concerns or questions about measles to call Healthline on 0800 611 116 at any time. Interpreters are also available. You can choose to speak with a Māori clinician if you're calling between 8am to 8pm.
Dr Rainger said parents can check their children's immunity by looking in the blue Well Child Tamariki Ora or Plunket Book Child Health or Plunket book or asking their medical centre.
To find out more about vaccination providers in your area, visit: Healthpoint.
