Combined with the estimated 1.5 million Pfizer vaccines the Government has already purchased, that means every New Zealander will have access to the Pfizer vaccine.
"The decision to make Pfizer New Zealand's primary vaccine provider, was based on the fact the Pfizer vaccine has been shown to be about 95 per cent effective at preventing symptomatic infection," the Prime Minister said.
Asked how much more New Zealand was paying for the Pfizer vaccine, Ardern said no matter what the vaccine was, it came at a "much lower price than the loss of life".
Covid-19 Response Minister Chris Hipkins said moving to only one vaccine meant the rollout would be "more efficient".
Ardern said she has been told that supply for the vaccines, including more freezers, "shouldn't be a problem".
On the issue of sportspeople, such as the Black Caps cricketers and Olympic athletes, receiving the vaccine, Ardern said officials would be "weighing up all the factors".
'The year of the vaccine'
Ardern said she has called 2021 the "year of the vaccine" and said the Government was making good progress on this.
The Government will share an updated vaccine rollout plan on Wednesday.
She said vaccines will be an important part of New Zealand's defence against the "tricky" Covid-19 virus.
"It's not going to slow our timetable at all," she said when asked if the Pfizer strategy would slow the rollout down.
Ardern said the Government had been able to take a step back and look at what vaccines had worked well around the world - that had helped influence the Pfizer purchase decision.
She said there were still other brands of vaccine that had been purchased, but they might be shifted out for use until 2022.
"Every country is going to take their own approach," she said on the vaccine rollout.
Hipkins said the Government was not looking at increasing the length of managed isolation stays at this stage, despite evidence that the UK variant tail was longer.
One border worker told Ardern that Covid-19 had "taken a toll on us all" and they were grateful for the vaccine being offered to them first.
New Zealand's previous approach was to secure a portfolio of vaccines and the other vaccine provider agreements were still in place.
"No countries are safe until all countries are safe," Ardern said on donations of vaccines to the Pacific.
Govt's confidence in Pfizer vaccine
Covid-19 Response Minister Chris Hipkins said the purchase confirmed the Government's confidence in the Pfizer vaccine.
yet to unveil a concrete vaccine rollout schedule.
Health officials are now working with Pfizer on a delivery schedule but Hipkins said the rollout will begin "from the middle of this year".
He also said that the Government is working on options for the vaccines which don't end up being needed in New Zealand.
"We are working on options for donating surplus doses across our wider portfolio to the Pacific and developing countries worldwide."
Hipkins said the Government wanted to ensure that any doses not needed here were put to good use elsewhere.
That could mean delaying delivery to New Zealand, in order to free up supply for other countries in the short-term, or donating spare vaccines to other countries, Hipkins said.
"We are also working closely with the Realm countries of Niue, Tokelau, and the Cook Islands, as well as our close neighbours Samoa, Tonga and Tuvalu to provide access to our vaccine portfolio and provide wider support for vaccine roll-out," Hipkins said.
On the Meghan Markle TV interview with Oprah Winfrey broadcast overseas today, which revealed she and Harry had considered moving to New Zealand, Ardern said that was never officially floated.
She said she had contact "here and there" with Markle but what was raised in the Oprah interview were matters for "Meghan and Harry".
Ardern said she had not sensed an appetite from New Zealanders that it should become a republic.
Ardern explains decision to pull out of weekly Mike Hosking Newstalk ZB interview
Earlier today Ardern's office confirmed she had ended her weekly interview with Newstalk ZB's Mike Hosking. Ardern told reporters this afternoon that she had communicated this message four weeks ago.
She said no one can do every slot: "People get news from a number of different sources".
"I don't think anyone would argue that I'm not available."
She said she had held press conferences and 21 interviews over the past week.
But she said she is looking to reach more people with her interviews.
Instead of fronting up for the weekly slot, as she has done since 2017 and her predecessors have done long before that, Ardern will now be appearing on the show "as and when issues arise".
This prompted Hosking to say Ardern was "running for the hills" and refusing to be held to account.
"Without being too unkind to some of the other players in this market, the reality is the Prime Minister enjoys a more cordial and more compliant relationship with them," he said this morning.
Ardern will be pressed on this issue by reporters this afternoon, when she faces questions from the press gallery after her weekly Cabinet meeting.
But the focus of much of her comments will be on new Covid-19 vaccine developments. She will provide an update on the vaccine rollout.
New Zealand is now more than two weeks into the mass-jab programme as so far more than 10,000 frontline Covid-19 workers have received the vaccination.
There are roughly 12,000 people in that cohort – after them, their 50,000 close contacts will get the vaccine.
Last week, National leader Judith Collins called for more clarity around the Government's vaccination schedule.
"Unlike other countries, New Zealand still has not published a detailed list of how the population will be prioritised for vaccines and when each group will be getting them."
Ardern has previously said that the reason for this was that the timetable of when the vaccines would arrive in New Zealand was up to Pfizer – the company the vaccines are being bought from.
At this stage, she said the rollout for the general population would begin "midway" through this year.
Meanwhile, health officials this afternoon reported there were no new cases of Covid-19 in the community.
But there were six new cases of the virus in managed isolation.
Health officials maintain the public health risk is low from the case of an Air New Zealand crew member who tested positive because she had limited contacts.
The woman has been transferred to the Jet Park quarantine hotel. Everyone in her household has tested negative and all are in isolation at home.
Officials now consider the most likely scenario was the woman was exposed to Covid-19 overseas and so was either incubating - or infectious - with the virus before she was vaccinated late last week.
And police have also been called in to help search for one gymgoer yet to be tested after the Papatoetoe Covid outbreak, the Ministry of Health says in today's update.
"One person from the gym remains outstanding and health staff are working with other agencies including police to try and contact this person," the Ministry said.
