The ability to contact-trace quickly and comprehensively can be as good as a vaccine, the Epidemic Response Committee heard on Tuesday.
But with only four days to go before lockdown D-Day, there is precious little information about contact-tracing capacity beyond the reassurances of PM Jacinda Ardern and health chief Dr Ashley Bloomfield.
Along with border restrictions and more testing, the Prime Minister has highlighted contact-tracing as one of the three key pillars of how New Zealand can win the "marathon" fight against Covid-19
If it's not up to scratch, lockdown could be extended, and the chances are greater of reverting to alert level 4 in future.
The dearth of information about contact-tracing has not been without very public questions about capacity.
The day before we went into lockdown, infectious diseases expert Dr Ayesha Verrall said the Health Ministry needed to be able to trace the contacts of 1000 Covid-19 cases a day - or 20 times the capacity at the time - by the end of the lockdown.
Following further public clamouring for more information from the likes of expert epidemiologists Sir David Skegg and Professor Michael Baker, the ministry eventually released a statement trumpeting its new national contact-tracing centre, which had traced 700 close contacts in a single day.
But there was no mention of how long it took to trace all the close contacts of a new Covid-19 case, the key measure in how quickly a new outbreak can be isolated and contained.
On Tuesday, the Epidemic Response Committee heard from Australia's top health official about Australia's ability to contact-trace within three days.
Asked how long it took in New Zealand, Bloomfield had no answer.
(Curiously, though, Bloomfield later told reporters that New Zealand was "at that capacity now", adding that he was "confident in the extent of and the pace of our contact tracing".)
Ardern and Bloomfield deserve praise for fronting media conferences almost daily, but this is not the first time the Government's confidence seemed to lack evidence.
When Ardern was being pressured, again by public health experts, to impose a blanket quarantine on all overseas arrivals, she said repeatedly that self-isolation was working well - but it remains unclear what she was basing that on.
More than 7000 foreigners arrived in New Zealand and were supposed to self-isolate in the four days before Ardern realised it was inadequate and shut the borders to all non-Kiwis.
Despite repeated questions, the Health Ministry cannot say how many of them were checked on since arriving, nor how many non-Kiwi cases of imported Covid-19 might have been avoided if Ardern had decided to shut the borders from March 16 instead of March 20.
Ardern's rhetoric about "successful" self-isolation was then shaken when then-police boss Mike Bush admitted that the compliance checks weren't happening as promised. Asked how many spot checks had taken place, he couldn't say.
There has been similar distance between rhetoric and reality with regard to PPE (personal protective equipment), flu vaccines and testing kits. Every day we are told that there are plenty of these supplies to go around while stories continue to emerge about scared and frustrated frontline workers' inability to access them.
The claims of shortages have become such an issue now that the ministry is taking steps to nationalise distribution.
Other times we've had to wait for the detail behind the rhetoric. It took almost two weeks for the Prime Minister to release the modelling about potentially tens of thousands of fatalities, a number she used to justify the lockdown.
Bloomfield was also repeatedly asked about gaps in the testing data before the Health Ministry eventually started to publish the breakdown of which ethnic groups and regions were being tested.
The ministry is not trying to be secretive and it should be noted that it is dealing with an enormity of data and media queries in unprecedented times.
It is also trying to find the right balance of releasing information quickly but ensuring it can be trusted.
Publishing false information undermines the credibility of the whole health response, and the ministry will be acutely aware of the apology it has already given for breaching the privacy of two people with Covid-19.
Bloomfield insists that contact-tracing data will soon be available and that the delay is down to moving the entire system from regional public health units - described by him as a "local cottage industry" - to a national system.
The importance of contact-tracing and the dwindling timeline until lockdown D-Day have now added extra weight to Ayesha Verrall's audit of the ministry's contact-tracing processes.
Her report, already in the hands of ministers and set to be released today or tomorrow, will shine a light on an area that has been and continues to be shrouded in darkness.
The value of independent oversight did not appear lost on Chief Ombudsman Peter Boshier, who said yesterday that he would look at whether aged-care facilities were doing all they could to block Covid-19.
Bloomfield has praised the sector for the relatively few number of facilities where an outbreak has occurred, but he is also commissioning his own review into the six premises where there are Covid clusters.
Boshier will look at the entire sector across the country.
His work and Verrall's are vital steps towards putting some meat on the bones of the Government's rhetoric.