COVID-19: 'Other countries' have told New Zealand not to use vaccination targets for easing restrictions - Jacinda Ardern

New Zealand is bracing for another significant COVID-19 update from the Government on Monday afternoon - a day after the country reported a big spike in cases mostly in Auckland.

Prime Minister Jacinda Ardern will at 4pm reveal restriction updates for Auckland, Northland and parts of Waikato - all of which are at COVID-19 alert level 3.

Northland was the latest region to be plunged into a snap alert level 3 lockdown on Friday - after a woman apparently used false travel documents to enter the region and subsequently tested positive for the virus.

Ardern said there's a lot to consider about whether to ease restrictions, especially when it comes to Auckland - which remains the epicentre of the Delta outbreak.

"[We'll] look at the cases… look at vaccination levels," she said.

The AM Show host Ryan Bridge asked Ardern if there was a vaccination percentage target in Auckland where restrictions could ease further.

"We will take into consideration two things; vaccination rates, we already know they are making a difference - they have reduced this outbreak by up to 50 percent, according to some modelling," Ardern said.

"The second thing we'll take into account is the outbreak itself; the numbers that we see, our ability to continue to control it - we've still taken the same approach today that we did on day one. We aggressively contact trace, we aggressively try and manage.

"In the many other conversations I've had with other countries who have used targets, they've all said to me, 'Don't use targets,' and one of the reasons is because they've found that when they've reached those places, they haven't necessarily been in the right place to remove [restrictions].

"Or, who knows? There may be circumstances in which we could move earlier," she said.

Earlier this year, the UK set a date for lifting COVID-19 restrictions in June - but delayed it to July 19 due to rising cases driven by the Delta variant - the strain currently circulating in New Zealand. 

But Sydney has pushed ahead with reopening without delay - officials keeping their promise to ease restrictions after meeting the threshold of 70 percent vaccination. The Australian city was in lockdown for 100 days. 

Just 55 percent of New Zealand's eligible population is fully vaccinated against COVID-19 but Ardern is confident the country will reach 90 percent - a target set out by officials last month.

New Zealand needed to continue its vaccination rate momentum, Ardern said. The latest Ministry of Health data shows 82,000 people received a vaccine dose on Saturday alone.

Another thing being discussed at Cabinet is whether Auckland students could return to school next week, Ardern told TVNZ's Breakfast.