Public health officials say they have contacted around half of the people who they believe may have been close to a child infected with measles.
The child arrived in Auckland on Malaysia Airlines flight MH131 from Kuala Lumpur on Thursday 26 February.
A team of doctors and nurses are now in the process of contacting hundreds of people who were either on the same flight, or who have spent time near the child since then.
Blood tests are being organised for people who cannot remember if they are immunised.
Medical Officer of Health Julia Peters said she hoped everyone would have been contacted by the end of today.
"We estimate there are probably around 200 close contacts, we have done around half of those and the rest will be done today. Approximately 50 percent are from contact in New Zealand and 50 percent are from the flight."
Dr Peters said none of the people they had contacted had reported any measles symptoms, but they would continue to monitor the situation.