A disease modeller has described the "confronting" moment he first realised how many New Zealanders could die from COVID-19. 

Shaun Hendy worked with the Government to develop its COVID-19 response. Now, one year on from New Zealand's first lockdown, Hendy told the AM Show the worst-case scenario would have been devastating. 

"The worst-case was like if we treated it like the flu, and that was around 80,000 deaths and… if we looked back and we tweaked the model given what we know now that is still actually the worst-case scenario." 

"The worst bit was when I actually first ran the numbers and just looked at them myself but then having to go and tell the rest of the country about that was quite confronting."

Hendy said thankfully, the Government acted quickly and New Zealand avoided thousands of deaths. 

On March 21, 2020 the Government introduced the 4 tiered system and two days later Prime Minister Jacinda Ardern plunged the country into lockdown. Thanks to the strict lockdown and border closure, New Zealand survived relatively unscathed with 2453 cases and 26 deaths. 

Hendy said the Government has successfully managed the pandemic so far, but we aren't out of the woods yet. 

"We've still got to get through this year and obviously looking forward to when the vaccination programme gets going in earnest," he said. 

New Zealand's vaccine rollout has already begun with border workers, however regular Kiwis will have to wait until later in the year prompting concerns over another outbreak as the weather cools down. 

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Hendy said while winter does pose a risk, vaccinating the border workers will help prevent it from getting into the community.

"[COVID] does better in winter and we've seen that in the northern hemisphere this winter. It's certainly a risk for us." 

"The vaccination programme at the border actually does help, we know that the Pfizer vaccine specifically is very good at blocking transmission so that will actually reduce the risk of more border breaches."

The Government has purchased enough of the Pfizer vaccine to inoculate every New Zealander. The vaccine rollout has been split into four groups with border workers and their families in group 1. Vaccinations for group 1 have already started. 

Group 2 includes frontline workers and people living in high-risk settings, beginning with healthcare workers on community frontlines, and then moving through to healthcare workers protecting the most vulnerable and some priority populations.

Group 3 is the priority populations including people who are at higher risk if they catch COVID-19. Vaccinations for group 3 are planned to start in May.

Group 4 is the remainder of the population and vaccinations will start from July.