Every New Zealander will be able to get a Covid-19 vaccination with 15 million doses now secured with the roll-out planned to begin in the second half of next year.
The Government is also working "very closely" with Australia to secure roll-out across the Pacific, said Ardern.
The Government revealed it has secured two additional vaccines.
The new vaccines are AstraZeneca - 7.6 million doses for 3.8 million people - and Novavax - 10.72 million doses, enough for 5.36 million people.
If the rollout goes to plan, there is enough for every Kiwi and to supply New Zealand's Pacific neighbours with the Government planning to secure vaccines to cover the Realm of New Zealand - Tokelau, Niue, Cook Islands.
It will also source enough to cover Samoa, Tonga and Tuvalu should their governments wish to take these up.
The vaccines will be free for all Kiwis.
The vaccines cover three different types of technology through the agreements with four manufacturers:
- 750,000 courses from Pfizer/BioNTech;
- 5 million courses from Janssen;
- 3.8 million courses from the University of Oxford/AstraZeneca; and
- 5.36 million courses from Novavax
Prime Minister Jacinda Ardern unveiled the Government's vaccine strategy alongside the Health, Covid-19 Response and Science and Research Ministers at the University of Auckland's medical research campus.
The first priority will be border workers and essential workers who are expected to get the vaccine in the second quarter of 2021.
Those workers include the border and MIQ workforce, the Covid-19 frontline healthcare workers and their household contacts.
The plan is to then vaccinate the rest of the general public throughout the second half of next year, dependent on speed of manufacture and sign-off from Medsafe which is developing an expedited approval process.
"We are moving as fast as we can, but we also want to ensure the vaccine is safe for New Zealanders," said Ardern.
Researchers were investigating how long the antibodies lasted for and she anticipated there would be more information available next year about ongoing vaccination programmes.
"Never before has the entire globe sought to vaccinate the entire population at the same time. This will be a sustained roll out over months not weeks but our pre-purchase agreements means New Zealand is well positioned to get on with it as soon as it is proven safe to do so."
Ardern said most countries were factoring the roll out to take all of 2021 and some of 2022 due to its scale, complexity and due to production and delivery timeframes.
Ardern said the countries granting emergency approval for vaccines were those facing public health emergencies and mounting death tolls and New Zealand was not in that position.
"We are obviously in an entirely different situation here."
Ardern said "much is unknown" about vaccines and a lot of work had gone into back-up provisions and any extras could be on-sold or donated to other countries.
Pfizer, as the first cab off the rank, was in hot demand but no country had secured enough of it to cover its entire population, Ardern said.
Ardern said the Government hadn't been specific with timings because they were reliant on timetables from the drug manufacturers.
The Government anticipated some vaccines not being delivered which was why it had purchased so many doses and options.
Minister of Research, Science and Innovation Megan Woods said the Government's vaccination strategy was to not put all its eggs in one basket as there were no guarantees they would all complete clinical trials or be rolled out successfully.
"Our plan is to ensure no-one misses out, even if it means we've purchased more than we need. It's an investment worth making," said Woods.
"The world of vaccine development is dynamic. While we're confident our four agreements place us in an excellent position, we're not ruling out other purchases if required."
Woods said the four vaccinations secured by the Government were complimentary to each other.
"Our purchasing strategy was deliberate," Woods said.
The Government drew on a panel of vaccine experts who put together the strategy.
Covid-19 Response Minister Chris Hipkins said preparations were underway to prepare for New Zealand's largest ever immunisation programme.
There are about 12,000 health professionals able to administer vaccines and the Government is planning to train more.
Hipkins said the vaccination programme would require "a huge logistical effort" - including the Pfizer vaccine needing to be stored about -70C.
The Government particularly wanted to focus on creating a diverse workforce to administer the vaccine, Hipkins said.
It would depend on logistics as to how many more people needed to be recruited to the workforce.
The new National Immunisation Solution (NIS) which was developed this year following the measles outbreak will be used by the Ministry of Health to track inventory with information about where doses are located and at which temperature they're being kept.
Concerns were raised this year ahead of the flu vaccination rollout with some GPs quickly running out while vaccines sat unused on pharmacy shelves.
Hipkins said the NIS would allow health officials to track and trace Covid-19 vaccines and consumables, including their expiry dates which would reduce wastage.
As well, the Health Ministry has purchased nine large -80C freezers that can store more than 1.5 million doses of the Pfizer-BioNTech vaccine which are set to arrive by the end of the year.
Health Minister Andrew Little said the aim of first vaccinating frontline health workers was to further strengthen the border and "create a layer of protection around the country".
Vaccinating this group will start in the second quarter of 2021, followed by general population - in stages - from the third quarter.
"We're factoring into our planning a large number of complex and interconnected individual strands, including the safety approval process, global supply chains, as well as lead-in times to manufacture and ship vaccines in bulk quantities," said Little.
It was "absolutely vital", Little said, that there was good coverage of the vaccines in the community.
The Government would be reaching out to Kaupapa Maori providers to ensure communities which normally experience poor access to healthcare are included in the vaccination programme.
The vaccines will be voluntary but Little said the Government would be sending out some "very strong messaging" about the vaccines.
Medsafe has agreed to allow pharmaceutical companies to make rolling applications for their Covod-19 vaccines so they can submit their data as it is completed and ready for assessment to speed up the process.
"Pfizer and BioNTech and Janssen have already started to submit data, and timing around Medsafe's approval process depends on many factors, such as the data that companies provide and whether it meets internationally agreed criteria for safety and efficacy.
"Medsafe has streamlined its assessment processes and is prioritising the assessment of Covid-19 vaccines over other pharmaceuticals to obtain a vaccine more quickly, but there will be no compromise on the safety of the vaccine. Medsafe will remain in close contact with its Australian counterpart throughout."
The Government has also provided details of how it plans to support New Zealand's Pacific partners and neighbours.
It will use $75 million of Official Development Assistance to fund the roll-out.
And $10 million of that fund will be a further contribution to the Covax Facility Advance Market Commitment which supports equitable access to vaccines.
Foreign Affairs Minister Nanaia Mahuta said New Zealand's approach will be to purchase sufficient vaccines to cover the Realm of New Zealand (Tokelau, Niue, Cook Islands) and our Polynesian neighbours (Samoa, Tonga, Tuvalu) should their governments wish to take these up.
Confirmed $75 million of Official Development Assistance had been earmarked to support Pacific and global vaccine access and roll-out.
"New Zealand is pursuing a portfolio of potential Covid-19 vaccines to ensure we have flexibility and choice in the fast-moving global marketplace. We want to make sure Pacific countries can also access suitable options, and have the support they need to run successful immunisation campaigns."
They allege the Crown ignored Treaty obligations by not engaging with them.