The outbreak of measles in the Canterbury is being made worse by the nation's low levels of immunisation, a health official in the region says.
Four students from Christchurch Boys' High School have the infection and another six teenagers or children are likely to have it.
The boys who are unwell were being isolated at home, and their family and close contacts were being advised to stay at home for several days unless they have had immunisations.
Canterbury Medical Officer of Health Dr Cheryl Brunton says New Zealand's immunisation level of 82% is well below international standards and most of those now unwell have not had the measles, mumps and Rubella injection.
"It is of concern, because if there are other un-immunised people in the population, then those people are at risk," she says.
Dr Brunton says she respects people's views on whether to have their children immunised but given the illness is present, they may want to reconsider their decision. She says people of any age can be given the measles vaccination by their GP.
Christchurch Boys' High School is closed for the holidays. Pupils are being told to see their doctor if they have any symptoms of measles.