Health officials dealing with measles outbreaks say low immunisation rates of people born in the 1980s and 90s may be to blame.
Following an outbreak in Waikato, four cases of measles have also been reported in Northland, and one in Nelson -all linked to the Waikato outbreak.
95 percent of under-fives have been immunised. Photo: 123rf
But why, when the country is achieving the highest ever immunisation rates, are there outbreaks?
The Ministry of Health's Chief Advisor on Child and Youth Health Pat Tuhoy said the problem was with those born in the 80s and 90s, who had an immunisation rate of between 80 and 85 percent - significantly lower than today's rate of nearly 95 percent.
"The reason we see outbreaks is to do with what we call community immunity, and measles is one of the most infectious viral diseases known, and in order to prevent outbreaks we need somewhere around 90 to 95 percent of the population to be immune."
Measles is commonly thought of as a childhood disease, identified by a blotchy red rash and fever. But the highly contagious virus, which can cause ear infections, brain damage and, in extreme cases, even death, can strike anyone.
Following a push over the past eight years from the government and medical sector, 95 percent of children aged under-five are now immunised leaving them at less risk of contracting measles than teenagers and young adults, born at a time when immunisation rates were lower.
Those aged over 50 are likely to have been exposed to the disease when they were young.
Immunisation Advisory Centre director Nikki Turner said the National Immunisation Registrar was started in 1997 and anyone born before that must rely on their own records.
Dr Turner said vaccinations had become a victim of their own success.
"Many people don't see the diseases, so one of the most common myths is that measles is a mild disease and that if you gave your child good nutrition, plenty of vitamins they wouldn't get severely ill from measles.
"I think really the biggest problem we have with vaccination programmes is out of sight out of mind."
Nearly 95 percent of children aged under-five now get their measles immunisations. Photo: 123RF
Health Minister Jonathan Coleman said he had not received any advice about a targeted programme to capture those unvaccinated young people.
But he said neither the government, nor health officials, wanted to see more outbreaks like that in Waikato.
"Regardless of what we might do in the future, the key message is that people need to get their children immunised."
However, some parents refuse to have their children immunised.
Dr Turner said they make up about 2 percent of the population and are generally safe because the vaccinated majority prevents the spread of infectious diseases.
Otago University's Professor of Biomedical Ethics Grant Gillett said that herd protection meant there was no need to compel all parents to immunise their children.
"There are a group of people who are inclined to be a bit contrary in relation to medical things.
"The difficulty with changing their mind is they've got this prior belief that the establishment is kind of a bit of a conspiracy."
A since discredited 1998 research paper by British doctor Andrew Wakefield linked the measles, mumps and rubella vaccine to autism.
Professor Gillett said in the face of such irresponsible science, doctors were justified in being biased in favour of children getting their jabs.
The Ministry of Health's advice for anyone in doubt about the measles, is to check your records and if you're not sure, get vaccinated. There is no risk of overdose.