Covid-19 initially threatened to kill thousands of Kiwis last year - instead, New Zealand's death rate finished up among its lowest in recent times.
A new study has also shown how a marked drop in deaths which came with level 4 restrictions was followed by historically low rates well beyond lockdown.
The Medical Research Institute of New Zealand-led (MRINZ) analysis, published in major journal The Lancet this month, explored trends 2020 death rates as far as mid-October.
It found lower rates that came after a sharp drop triggered by lockdown carried on through for nearly 30 weeks after.
"With a hard and fast approach to eliminating Covid-19, we were interested to find out what effect it might have had on overall mortality rates," lead author Dr Stacey Kung said.
Using mortality data from Stats NZ Tatauranga Aotearoa, the researchers compared the number of weekly deaths in 2020 with the average weekly deaths during the 2015-2019 and 2011-2019 periods.
To account for changes in population size over the years, numbers of weekly deaths were reported as per million population.
The year got off to a typical start, hovering close to 120 weekly deaths per million, before the trendline took a sharp turn around late April, five weeks after New Zealand moved to level 4.
Over the 29 weeks after the start of lockdown, the mean death rate was 11 per cent lower than the same period between 2015 and 19 - or 123 weekly deaths per million, compared with 138 deaths per million.
The drop across all causes of mortality became especially clear after five weeks of lockdown, and stayed low despite public health intervention measures easing, and in a period where seasonal flu and pneumonia usually drove an increase.
"The continued decrease in weekly all-cause mortality, even after New Zealand had moved to Alert Level 2 and subsequently 1, is striking," Kung said.
"It would be reasonable to expect that as life returned to normal, the weekly death rate would go back up to historical levels.
"At the time of publication, we didn't have access to information about the specific cause of deaths in 2020 - so we could only speculate the reasons as to why the death toll was lower."
Other studies have pointed to the fact that only 500 cases of influenza were detected up to September 27 - and 474 of them were recorded before lockdown.
"Adhering to good hygiene practices evidently helps to reduce not only the transmission of Covid-19, but also helps to reduce the transmission of the flu – with very few influenza hospitalisations reported last year," Kung said.
More than 200,000 New Zealanders catch the flu each year, and an estimated at least 500 people die from it.
That accounted for 2 per cent of all deaths, and was more than the annual road toll - which last year proved to be lower, too.
Ministry of Transport provisional figures show 320 people were killed on our roads in 2020 - 32 fewer than in 2019.
In its own reporting, Stats NZ Tatauranga Aotearoa stated alert level restrictions - along with limits on road and air travel and temporary business closures - may have partly explained the 1,680 fewer deaths registered between March and September, compared with 2019.
Kung stressed it was still too early to say conclusively what the wider consequences of New Zealand's public health measures were - but it was clear it delivered strong results.
"While the public health interventions used were not novel or specific to New Zealand, the clear communication with the public and strong leadership meant that all New Zealanders were on the same page and aware of expectations and policies implemented by the government," she said.
"Unfortunately, that wasn't seen in countries such as the US or the UK, which continue to grapple with the pandemic."
In a separate study, just published in the European Respiratory Journal – Open Research, Kung and her colleagues also looked at all-cause death rates in more than 20 other nations - particularly where the virus had spread far.
Compared with the five years before, the researchers found there were more than 716,000 extra deaths in the countries included in the analysis - with Covid-19 attributed to around two thirds of those.
In most countries that had spikes in Covid-19-related deaths, the analysis found increases in all causes of deaths came before the increase in Covid-19 reported deaths.
"The key finding was that the number of deaths attributed to Covid-19 was underestimated by at least 35 per cent," Kung said.
Research suggests that this could have been due to Covid-19 deaths being misclassified, such as deaths being incorrectly attributed to heart disease and cerebrovascular disease.
"Together, these findings suggest that the calculation of excess all-cause mortality is a better predictor of Covid-19 mortality than the reported rates, in those countries experiencing definite increases in mortality."