The Ministry of Health has dropped its "gold standard" of notifying at least 80 percent of potential contacts within 48 hours of detecting a new case of COVID-19.
Associate Health Minister Dr Ayesha Verrall says the goal is no longer applicable to the current scale of contact tracing, which is now operating at an "industrial" level.
Almost 300 potential exposure sites have been identified since the beginning of this latest outbreak, including a number of crowded venues such as bars, malls, and supermarkets - as well as several highly populated schools and universities - across Auckland, but also in the Coromandel, Wellington, and several small towns in the central North Island.
Around 10,000 contacts have been linked to the current outbreak, indicating that potentially large numbers of people have been exposed to the virus - the highly transmissible Delta variant, which is wreaking havoc overseas.
Speaking to The AM Show, Dr Verrall said the sheer numbers - plus the transmissibility of the Delta strain - are making it difficult to stick to the previous goal.
"We've been going over some of those metrics, which were metrics that came from my report last year - in light of the changing situation, there's a couple of things to think about with that. One is when we're doing this wide-scale, locations of interest tracing - we have 10,000 people in the contact tracing system. We're working in a slightly different mode here," she told The AM Show.
"The other thing is Delta does also change many of those goalposts that I set previously. Previously I had said we could turn around an outbreak with contact tracing alone - I think for Delta, that actually isn't possible anymore, and we do need to be at high alert levels while we do contact tracing."
However, the Associate Minister of Health could not provide a new tracing target based on the current volume of contacts.
"We are doing industrial-scale contact tracing with these locations of interest, and in that situation, some of the reporting issues need to be worked through - some of the data issues there," she said.
Host Ryan Bridge noted that the country is now entering day six of its alert level 4 lockdown, but health officials still don't know how well its staff are performing in regards to contacting those who are potentially infected with the virus.
"I don't have that data today, but I can tell you that for the people who are household contacts of the known cases, we have a high rate of completion," Dr Verrall said.
"I think you'll see a whole lot of things that support how well the contact tracing is happening… I think the contact tracing is performing well. But we don't have a report on the timeliness of that [tracing]."
On Sunday, the Ministry of Health reiterated its public health staff were focusing their contact tracing efforts on "higher risk locations" as the number of contacts "increased significantly".
As of 9am on Sunday, 8667 individual contacts had been identified, a number which was expected to increase throughout the day as more records were fully processed. The majority were close contacts.
Of these 8667 contacts, just under half - 4124 - had been contacted and were self-isolating, or about 47.6 percent, and a third had been tested.
"Work is underway to contact the remaining 4500 contacts. Most of these contacts were identified yesterday as a result of case investigations into settings with high numbers of people involved, [such as] schools," the ministry said.
The sheer scale of the potential exposure sites has also cast doubts on whether the South Island, which so far remains unscathed by the current outbreak, could be released from lockdown as of Tuesday.
When asked whether the southern regions might be able to shift to level 3, Dr Verrall again noted the significant number of potential exposure sites, and the fact that not every contact can be identified.
"We also know that maybe in the time from when [Case A] was first ill through to when Auckland went into lockdown, tens of thousands of people left Auckland to destinations all around the country - so we know some of the contacts, but we may not know every case where every exposed person went in New Zealand. So that's the risk we are cognizant of when considering alert level changes."
Cabinet are set to convene on Monday to discuss the next steps for New Zealand's lockdown, which remains in place nationwide until at least 11:59pm on Tuesday.
She reiterated that as seen in previous lockdowns, "things get worse before they get better", and it is possible that New Zealand will see a higher number of cases on Monday than in previous days.
The current outbreaks now stands at 72 cases, 42 of which were reported over the weekend - 21 on Saturday and Sunday respectively. Sixty-six of the cases are in Auckland and six are in Wellington. Sixty-one of the cases have been definitively linked to the Auckland cluster, while 11 remain under investigation.
The outbreak has been linked to a Sydney returnee who arrived in Auckland on August 7 and tested positive just two days into their stay at the Crowne Plaza managed isolation facility. The returnee later became unwell and was transferred to Middlemore Hospital on August 16 for treatment. However, it's still not known how the virus was passed from the returnee to Case A, the first case in the outbreak - an unvaccinated Devonport man in his 50s.
