New Zealand's regulator has cleared three COVID-19 vaccines for use but Jacinda Ardern's government is only planning to use Pfizer.

New Zealand will fast-track vaccine to the Pacific, and consider incorporating AstraZeneca in its fight against COVID-19 after the vaccine received the regulator's signoff.

Medsafe has now approved three vaccines for use in New Zealand - Pfizer, Janssen and AstraZeneca.

However, Jacinda Ardern's government has committed solely to Pfizer for its initial vaccination program, which has been criticised as slow and leaving New Zealand at risk.

As of this week, just 700,000 Kiwis are fully vaccinated and 21 per cent have received one dose of the two-dose Pfizer vaccine.

The approval of Janssen and AstraZeneca could theoretically boost supply, but Associate Health Minister Ayesha Verrall said New Zealand was likely to stick to script.

"We have a plan for two doses for every eligible New Zealander with Pfizer (by the end of the year)," she told AAP.

"I haven't seen any evidence suggesting we should change from that.

"We've invested in the ultra-low freezers (needed for Pfizer) and other aspects and logistics of this program ... we considerably simplified our work by having a single vaccine."

Unlike Pfizer, which requires refrigeration at very low temperatures, AstraZeneca can be stored at fridge-like levels.

New Zealand signed a deal with AstraZeneca for 7.6 million doses - enough for 3.8 million people - last year.

New Zealand will divert some of its AstraZeneca, including through the international COVAX operation, to Fiji and the Pacific.

"We made a commitment that we will supply Fiji and every other country in the Pacific working with Australia," Pacific Peoples Minister Aupito William Sio told AAP.

"We can now be confident in making sure that Fiji has the supply needed to vaccinate their eligible population."

In committing to Pfizer, New Zealand has also dodged the ugly debates in Australia around vaccine preference, and the remote possibility of blood clots.

"It's important that we contextualize risks," said Dr Verrall, who was an infectious diseases physician before she entered parliament last year.

"The risk of COVID-19 in terms of hospital admissions, deaths and long-term consequences is far greater than any of the risks associated with any of our approved vaccines."