New Zealand in fresh Omicron scare

Central Auckland
There have been six confirmed cases of the Omicron variant of COVID-19 in New Zealand to date. -AP

Jacinda Ardern has warned New Zealanders to brace themselves for new daily COVID-19 case records when - and not if - Omicron runs loose in the community.

After a summer free of the ultra-transmissible variant, health authorities fear that moment may have arrived after two further positive results were reported on Wednesday night.

The health ministry issued an urgent release at 11pm confirming genomic sequencing results of an Auckland airport worker and a household member of a quarantine worker.

It has urged Tuesday lunchtime diners inside Ara Tai Cafe, a seaside cafe in the Auckland suburb of Half Moon Bay, to isolate immediately and get tested.

There have been six confirmed Omicron cases in New Zealand to date but so far there has not been documented community transmission outside of households.

Speaking from at Labour's year-starting caucus retreat near New Plymouth, Ms Ardern said Omicron's arrival was inevitable.

"We know Omicron is in every corner of the world at the moment," the prime minister said.

"We know that we will experience in New Zealand cases at a level we haven't experienced before.

"We face a different challenge with Omicron ... it is not insurmountable but it is a different foe.

"We know again the tools that will make a difference.

"Vaccination will change the game. For the most part, people will be able to recover at home. They won't experience severe disease and illness.

"That's not something we could have said in 2020."

With Omicron surging in Australia and other countries, cases are arriving in quarantine at record rates for NZ.

The seven-day rolling average of border cases has overtaken the same average of daily community cases, heaping pressure on the quarantine system.

Ms Ardern is eager to avoid Australia-style case numbers should Omicron eke out of quarantine, announcing a new plan to curb transmission of the variant.

Within 48 hours of the detection of an Omicron outbreak, NZ will shift from its current "orange" traffic light setting to "red", which caps indoor gathers and blocks unvaccinated people from many places and events.

"We know from other countries it can take as little as 14 days for Omicron cases to grow from the hundreds into the thousands," she said.

"The single most important thing New Zealanders can do to prepare for Omicron is to get their booster dose before it takes off in the community."

University of Otago public health professor Michael Baker said he was "very concerned" Omicron would take hold.

"We've had three of these near misses through different pathways," he told Radio NZ.

"A huge driver is the really large number of infected cases in New Zealand. We've never had such pressure on our borders.

"We need to reduce the flow of infected people into New Zealand immediately."