New Zealand will almost certainly have a significant measles outbreak this year, public health experts say.

And there are fears very young children will die.

Measles cases are growing globally, with a 45-fold increase in Europe in the past year and hundreds of cases in Britain since October.

Otago University epidemiology professor Michael Baker says New Zealand is in line for a significant outbreak.

"I think it is almost certain unless we do rapidly raise vaccine coverage, because the problem with measles is that it's so infectious you need very high coverage with not too many gaps in a population if you want to stop outbreaks."

An outbreak could be similar to the one in 2019 where there were more than 2000 cases and hundreds of people hospitalised, many of them under five, he says.

Māori Health Authority/Te Aka Whai Ora clinical director Rawiri McKree Jansen says many people are travelling between New Zealand and countries with active cases.

"Every public health physican, every population health expert I know agrees that it is almost certain we are going to get cases across the border and, given our low immunisation rates, we're at really high risk of having an outbreak."

Hundreds of children were hospitalised in New Zealand in the last outbreak, none died.

But since then, vaccination rates had fallen, he says.

"No expert I know says we're going to get through the next outbreak without seeing some tragic deaths of babies."

About 95 per cent of people need to be immune to achieve herd immunity for measles.

Ministry of Health figures show just 83 per cent of two year olds are up to date with their vaccines - which includes measles. For tamariki Māori, the rate is 70 per cent.

McKree Jansen says the health system has consistently underperformed when it came to delivering vaccinations to Māori children.

He urges health teams and parents to do everything they can to get them vaccinated.

New Zealand also has an immunity gap among tens of thousands of young adults who missed out on one or both vaccinations when they were children, many because of a problem with the system at the time.

A catch-up campaign has been under way for years to try to reach them.

Baker says the measles vaccine is in many ways a "dream vaccine", because two doses gives most people near-lifetime immunity, and if enough people are reached, it stops the spread of the virus through the community.

McKree Jansen says Te Aka Whai Ora is working with Māori health providers to reach as many unvaccinated people as possible.

Te Whatu Ora/Health NZ says it has a national response plan ready to go if an outbreak occurs, including an incident response team, which was mobilised six times last year because of cases which came over the border.

A spokesperson says in the largest incident then, it kept an outbreak contained to six cases.

Baker says it's important New Zealand does all it could to prevent the disease spreading to the wider region, with an outbreak in Samoa that killed 83 people in 2019, which likely spread from New Zealand.

-Rowan Quinn/RNZ.