"The vaccines are expected to arrive in New Zealand during the second half of the year," Prime Minister Jacinda Ardern announced on Monday. 

Ardern said 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 percent effective at preventing symptomatic infection.

"It also means all New Zealanders will have the chance to access the same vaccine," she said. "Whilst the Pfizer vaccine does need to be kept at ultra-cold temperatures, this challenge is offset by only having to deal with one vaccine, rather than multiple vaccines with multiple protocols."

She said it will "simplify" the vaccine roll-out. 

COVID-19 Response Minister Chris Hipkins said the Ministry of Health is now working with Pfizer on a delivery schedule for the additional vaccines. The general public is expected to start getting vaccinated from mid-year. 

"Consideration is also being given to how best to use vaccine doses that don't end up being needed in New Zealand," Hipkins said. "We are working on options for donating surplus doses across our wider portfolio to the Pacific and developing countries worldwide."

Hipkins said the Government is committed to ensuring that any doses not needed are put to good use elsewhere. 

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"Options could include 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," he 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."

The Government's purchase of additional Pfizer vaccines comes after Italy blocked the export of 250,000 Astra-Zeneca vaccines to Australia, using new European Union regulations in January allowing exports to be stopped if the company has failed to meet its contractual obligations. 

Hipkins said last week New Zealand has made clear the Government's concern at the European Union's export restrictions for COVID-19 vaccines manufactured in the EU. 

"It's disappointing to hear Australia is experiencing delays in the shipments of its contracted AstraZeneca vaccines from Europe," he told Newshub. 

"Vaccine manufacturing relies on global supply chains. It is in all countries' interests to ensure the smooth functioning of these supply chains, and actively facilitate the flow of COVID-19 vaccines and vaccine-related goods."

New Zealand's medicine regulator Medsafe is yet to approve use of AstraZeneca, and Hipkins said it expects to hear from the company this month about where it will be manufactured if it is approved. 

More than half of New Zealand's estimated 12,000 border workforce has now received their first vaccinations, as the third batch of Pfizer vaccines arrived in the country this week, the Government announced last week. 

But the Government is yet to provide a full roll-out plan. 

"I don't see any plan in place for the vaccine roll-out," National leader Judith Collins told Magic Talk on Monday. "If there is a plan it's clearly a secret plan and it's no doubt a very secret and cunning plan that we're not allowed to know about."

Ardern told The AM Show on Monday the vaccine deliveries from Pfizer so far are actually in "advance" of the Government's expectations. 

"You see for yourself, every week we give those updates on how we're tracking," she said. 

The third shipment of Pfizer-BioNTech vaccines last week added a further 65,500 doses, bringing the total number of COVID-19 vaccines in New Zealand to 200,000.