Jacinda Ardern has spoken to media at a new vaccination centre at The Cloud, joined by Ministers Chris Hipkins and Willie Jackson.
Watch the PM speaking here:
On reopening the borders, Ardern says New Zealand is in demand, and the government is learning and developing along the way.
She says the government has chosen to reopen at the specific time chosen to allow as many people as possible to have got their booster.
She encourages everyone to take up the opportunity.
Ardern says the reopening is based on several factors including the level of vaccinations, but the time of year also plays a role: "Because it is more likely that people are outside, easier to social distance, better ventilation, and all of that does help with management."
She says the government wants to make sure New Zealand continues to be an attractive place to come - including for tourists - because of the management of Covid-19.
"It's a constant balance but one I think we've got right."
Dr Ian Town, the lead on the clinical advisory team on vaccinations, earlier this week said there is not enough data to show conclusively whether the effects of booster doses wane in a similar way to getting two shots, she says.
She says there perhaps hasn't been such a high level of uptake with boosters and says overseas it's often the case people will be more urgent about getting the booster when Omicron starts to spread rapidly. She asks people not to wait.
With a larger number of cases expected, there won't necessarily be the same capacity in MIQ to care for incoming travellers as has been seen in the past. She says with home-isolation being brought in many travellers will however be able to isolate at home.
Ardern says the criteria for moving out of Red is quite straightforward: "We want to know that we are managing Covid within New Zealand in such a way that it's not placing extra pressure on our health system, that we're not seeing severe impacts on our vulnerable communities - so we constantly monitor that."
She says we are right at the beginning of an Omicron outbreak so Red is "the best place for us", but the government will keep an eye on the settings in future to see whether it's safe to move.
She says New Zealand is in a good position compared to many other countries on Omicron because of various factors - moving early with health measures and high vaccination particularly but the aim is to slow down the spread so the health system is not overwhelmed.
"Jury's a bit out because not too many countries have managed to slow it down but again, we'll continue to make decisions that are about ensuring New Zealanders continue to get the healthcare they need, when they need it."
Ardern is touring around Auckland after yesterday confirming the dates and planning for New Zealand to reopen international borders in stages.
It followed the announcement on Wednesday that the interval between second and booster doses of the Covid-19 vaccine would be reduced from four months to three.
That would allow an extra million people to get booster vaccinations this weekend, and vaccination clinics are planning for a large influx.
It would bring the total number of eligible people aged over 18 to more than 3 million, with hopes it would curb the spread of Omicron as New Zealanders start to return without MIQ from the end of February.