Low levels of immunity against measles among women of child-bearing age are putting babies at risk, warns one public health expert.
There have been 14 confirmed cases in the present outbreak, and more than 2000 close contacts identified.
Tairāwhiti Medical Officer of Health Dr Oz Mansoor said traditionally it was assumed that babies too young to be vaccinated would receive some protection from maternal antibodies.
"It was never perfectly true, but it seems to be less true now because of the shifting in maternal immunity," he said.
"Many mums will have zero immunity - they will have neither vaccine nor disease.
"They were brought up in the vaccine era, so they were less likely to be exposed to the disease, but they themselves didn't get the vaccine, so they've got no antibodies to pass on."
Under the National Childhood Immunisation Schedule, the MMR vaccine is given at 12 and 15 months.
The vaccine can be given under prescription to babies as young as four months if they are travelling overseas to countries with measles outbreaks, if they are close contacts or when there is uncontrolled community spread.
Young adults born from the mid-1990s and early 2000s were the most at risk of catching measles due to missed vaccinations, along with preschoolers born since Covid-19, due to access problems and rising vaccine hesitancy.
Many of those young adults - who were now having children of their own - may not even realise they had not had two doses of the measles, mumps and rubella vaccine (MMR) because they had been vaccinated against everything else, he said.
Persistent misinformation from the late 1990s suggesting an association between the MMR vaccine and autism had made many parents fearful of it, he said.
While the theory - based on a discredited scientific paper - was swiftly debunked, it had an ongoing impact on MMR uptake.
"The tinder keg we're sitting on is that we have well over half-a-million New Zealanders who are susceptible to measles."
All New Zealanders should be encouraged to check their immunisation records, he said.
Ask your GP or call the free Vaccination Helpline on 0800 28 29 26.
