That found there'd be an estimated 11,400 total hospitalisations - peaking with 324 active and 36 new daily cases in hospitals - and 1030 total deaths.
While a strategy targeting vaccination of high-risk groups would result in lower hospitalisations and deaths, it could also lead to a higher number of cases compared to a strategy targeting reduced transmission.
Lead author Professor Colin Simpson, of Victoria University, said the study aimed to predict how many people would need to be immunised for herd immunity, which age groups should be targeted first, and in what order.
It also looked at what the number of cases, hospitalisations and deaths would look like under various ranges of vaccine effectiveness and population coverage.
As well, it also took into account the varying reproductive numbers - measuring how many other people, on average, an infected person passed the virus on to - of different variants.
Worryingly, the modelling found that reaching the herd immunity threshold based on the rapid infection rate of the Delta variant was almost impossible.
When the researchers modelled the original strain of the virus, they found that, even if the vaccine was 90 per cent effective against disease - and 80 per cent effective against infection - New Zealand would require at least 86.5 per cent total uptake.
And that rollout would need to include all children - the vaccine has only just been approved for New Zealand children between 12 and 15 - and include high coverage among 30 to 49-year-olds.
Yet, against the Delta variant at the centre of this outbreak - and now the main variant in many countries around the world - an uptake of 98.1 would be required.
ESR chief scientist Dr Brett Cowan said the results showed that vaccinating as many New Zealanders as possible would reduce the risk of widespread community outbreaks and, as a result, vulnerable populations would have a greater chance of protection from severe disease.
But other public health and social measures would still be required as part of an effective pandemic response.
"Vaccination modelling has been proved to help anticipate potential public health outcomes based on different vaccine effectiveness reported in clinical trials and 'real-world' studies and vaccination programme strategies," he said.
"While the study was primarily developed with New Zealand in mind, our experience will also provide valuable insights to the international community to inform future actions."
Study co-author Andrew Sporle, of the University of Auckland, said it remained critical to include strategies that ensured maximum protection for Māori and Pasifika, who were at higher risk for hospitalisation and death from Covid-19.
"Prioritising vaccinations for those most at risk of severe outcomes from Covid-19 infection - including Māori and Pasifika - benefits the whole population as well as protecting those groups," he said.
"We know that opening the border will result in local cases of Covid.
"Minimising the resulting hospitalisations and deaths requires prioritisation of those groups and communities most at risk, as Australia and Canada have done.
"The risk of a border breach before our vaccination delivery is complete means that prioritisation must be a focus of the vaccine roll-out and not a catch-up strategy."
The new study, published in the Lancet Regional Health today, echoed the grim findings of earlier modelling by Te Pūnaha Matatini researchers.
That indicated that 83 per cent of New Zealanders would have to be vaccinated against less transmissable virus strains for measures like lockdowns and 14-day quarantine to be no longer needed.
It also suggested 97 per cent of Kiwis would need both Pfizer jabs to abandon such measures if the country was hit by a wave of a strain as transmissable as the Delta variant.
Hitting that level of vaccinations remained unlikely.
While the number of Kiwis who want to be vaccinated has been rising, as at June, the Ministry of Health's latest survey period, overall potential uptake of the eligible population was only about 77 per cent.
Last week, the Government announced it would use the second half of 2021 to vaccinate as many New Zealanders as possible, while carrying out a self-isolation trial for vaccinated travellers to prepare for a "phased resumption" of quarantine-free travel.
But just days later, plans for the trial were disrupted by another outbreak and nationwide lockdown.
