A total of 1327 cases of measles have been confirmed across New Zealand to date, with 1108 of those in Auckland.

The outbreak continues to rise, with 44 more cases in the Auckland region since yesterday - with 34 in the Counties Manukau DHB area, five in Waitemata, and five in Auckland.

With no sign of a decrease in the spread of the disease, the Auckland Regional Public Health Service (ARPHS) is changing tactics on how it addresses immunisations.

Up until now, the drive to get immunised has been pushed upon all those that have never been vaccinated, but now the strategy is now turning towards a more targeted approach.

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Medical officer of health Dr William Rainger said the strategy for managing the outbreak in Auckland still remained firstly to protect the most vulnerable.

"Vulnerable in terms of the likelihood of infection and vulnerable in terms of severity of disease, and that is the under 5-year-olds. So the first priority is for GPs to maintain the childhood immunisation schedule.

"The second objective is to interrupt the chain of transmission - which means looking at the data that we have about who is getting the disease, where it is being transmitted geographically, and trying to target the remaining vaccine supplies to those areas and those populations."

Auckland Regional Public Health Service (ARPHS) Medical Officer of Health Dr William Rainger. Photo / Jason Oxenham
Auckland Regional Public Health Service (ARPHS) Medical Officer of Health Dr William Rainger. Photo / Jason Oxenham

Rainger said the vaccination message had changed over-time due to the changing environment.

"We are now at a very high rate of disease occurrence and we need to be more targeted," he said.

"There is a finite amount of vaccine globally, and in New Zealand, so we do have to make those decisions about what is the most affective use of it."

In terms of the Auckland outbreak, the most prominent ethnicities affected by the disease are Pacifika and Maori, with children under the age of 5 the worst affected.

"It is those groups that we will be looking at with targeted outreach initiatives," Rainger said.

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He said the sorts of factors likely to be involved in the susceptibility of these ethnicities were immunisation uptake, housing conditions, and mobility between households.

Open community clinics have now been closed, and would be replaced by these targeted initiatives, such as at Pacific churches and certain employers.

Rainger said further national supplies of the MMR vaccine had also arrived in the country and would be distributed to regional suppliers and GPs later this week.

He said how long this supply lasts, depends on how much it is utilised.

"It is expected to last for the next three months - the next order is in January, but Pharmac is working to source more supplies from overseas."

He said the supply would be monitored on an ongoing basis to make sure it was being best used.

Rainger said there had been practices that had run out of the vaccine, but he believed the process to redistribute supplies had been "reasonably effective" and was ongoing.

When questioned on whether the initial reaction to the outbreak was incorrect, Rainger said it was difficult to predict how rapidly the outbreak would grow because of uncertainty about the number of vulnerable people.

"We tailor our advice based on the best available information and the best professional judgment at the time - it's extraordinarily easy to look back in retrospect and say we would have done things differently but I am confident it's been an appropriate response.

"So using the existing supplies to cover as many people as possible was not an unreasonable strategy at the time, and it would have had some benefit," he said.

"But we have now reached a stage where we have to look at the national situation, the supplies, and how to best use the available resources."

Rainger said the effectiveness of the targeted approach would determine the reach of the disease, and how long it effects the city.