Four cases of the measles in Northland have raised fears about a full-scale outbreak in the region, with the Northland District Health Board (DHB) saying more cases are expected in coming days.
The concerns were raised just two days after Morrinsville College in Waikato was closed when a student was found to have contracted the disease.
Northland DHB medical officer of health, Dr Claire Mills, says the recent pick-up in measles cases has worried them.
"Given these cases and the bigger outbreak in the Waikato region occurring now, it is very possible that we will see this outbreak extend across Northland," she said.
"Measles can be a very serious illness, with one in three sufferers experiencing complications such as ear infections, pneumonia, bronchitis or diarrhoea."
Vaccination rates in Northland currently sit around 90 percent for children under the age of two -- but many older children were not vaccinated as babies and will be at risk.
Dr Mills says while research suggests only one-in-10 will require a visit to the hospital, statistics from the more recent outbreaks show hospitalisation from measles is actually more likely.
And she insists vaccination is the ultimate protection from the disease.
"This is an avoidable disease where there is an effective vaccine," she said.
"Immunisation protects not only the individual, but also stops the spread of this disease within our communities.
"Vaccination is a much better option than having a very sick child at home for a couple of weeks, or having your teenager miss two weeks of school."