More than 400,000 people, mostly aged between 10 and 29, are at risk of catching measles in an outbreak, Health Minister Jonathan Coleman says.
He's highlighting the importance of being immunised against what he says is a highly infectious and potentially serious disease.
"The Waikato region is experiencing a significant measles outbreak," he said.
"Visitors to and from Waikato have led to further measles cases in the Nelson Marlborough, Northland and MidCentral DHB areas."
Dr Coleman says it affects children and adults, and low immunisation levels among certain age groups means outbreaks can spread.
"Measles is now rare in New Zealand thanks to immunisation ... but outbreaks like these are an important reminder for Kiwis to ensure they're immunised, or to check their immunisation status if they're unsure," he said.
"Over 400,000 New Zealanders, mostly between the aged of 10 and 29, are at risk of catching measles in an outbreak.
"Most older and middle-aged adults have already been exposed and are immune, and most young children have been vaccinated."
Dr Coleman says around 30 percent of people with measles will develop complications, and one in 10 may require hospital treatment.
Information about vaccinations is available at 0800 IMMUNE (0800 466 863) or Healthline (0800 611 116) and on the Ministry of Health website.