Two hundred Kiwis may have died had the Government held off ordering our nationwide lockdown for another three weeks - while nearly 12,000 people may have been infected.
That's the stark upshot of newly-published modelling that's underscored how crucial New Zealand's "go hard, go early" response to Covid-19 was in sparing the country a calamity - and putting it on path to elimination.
The paper, by researchers at University of Auckland-based Te Punaha Matatini, also suggested a slightly earlier lockdown may have spared several hundred infections - but added that might have been impractical at the time anyway.
The modelling took a sweeping look at New Zealand's initial approach to the pandemic, to find that the lockdown proved a much stronger driver in bringing down daily cases than border closures.
New Zealand moved to alert level 4 on March 25, before dropping back to level 3 on April 27, during a period the country registered just over 1500 cases and 22 deaths.
Nearly 11 weeks later, Covid-19 had been eliminated.
But had the shift to alert level 4 been delayed by 20 days, the country could have recorded more than 11,500 cases and 200 deaths - and slashed the chance of eliminating the virus to just 7 per cent.
The modelling indicated that Māori and Pacific people - who have a greater infection fatality risk - could have been disproportionately affected.
The delay would have also increased the chance of a longer lockdown period being needed to bring down daily numbers to low levels, given that authorities may have still been reporting 35 fresh cases around the time alert level 4 finished.
A much bleaker scenario explored was one where no lockdowns were put in place at all - potentially leading to two million reported cases and tens of thousands of deaths.
Conversely, moving to alert level 4 five days earlier could have resulted in 500 fewer cases, and 10 fewer deaths.
"However, in reality, the rapid escalation of the Covid-19 situation in mid-March may have made an earlier start to alert level 4 impractical and would have allowed less time to prepare for ongoing provision of essential services," the researchers added.
Further, they found introducing border restrictions requiring 14-day self-isolation for international arrivals earlier than March 15 would have been unlikely to have much impact on the trajectory of the March-April outbreak.
But that was unless such measures were started prior to the country's first case on February 26 and used methods that were particularly effective, such as managed isolation and quarantine facilities we have in place now.
Te Punaha Matatini director Professor Shaun Hendy said it was fortunate that the virus arrived in New Zealand comparatively later, and that the country was able to put itself in a position to eliminate it.
"A lot of countries have used lockdowns, but have eased off as people really got sick of them, and the pressure on Government came to move away from them," he said.
"Because we went early relative to where our epidemic was at, we were able to get to an elimination goal relatively quickly.
"That's had a massive impact on New Zealand on its own, so I think [lockdown] was absolutely the right call."
Hendy said Melbourne's experience offered a glimpse at what might have happened had authorities moved slower.
"We could have found ourselves facing a very, very long lockdown."
Although it wasn't factored in by the modelling, a rampant epidemic would have also been worsened by colder conditions of winter, he said.
"So us going into winter as opposed to the Northern Hemisphere going into summer, there was a big, big risk for us if we hadn't eliminated it."