Top epidemiologist Sir David Skegg says the loss of New Zealand's Covid-free "Shangri-la" is due in part to decades of public health neglect, as well as bad luck.
He also warned that contact-tracing capacity - which was severely stretched when case numbers were lower than they currently are - still needed to be strengthened, while the work to add saliva testing and rapid antigen testing to the toolbox had been slow.
And while he still hoped for New Zealand to continue to have a world-leading response, he feared an under-resourced health system will not be able to cope with whatever Covid throws at it in coming years.
Skegg spoke to the Herald exclusively as an independent expert, rather than from his position as chairman of a Covid-19 advisory group to the Government.
He has been warning to expect, and prepare for, a Delta outbreak since well before this one started.
"Whereas we had been lucky after several previous incursions of SARS-CoV-2, our luck ran out this time," he said.
The virus had a head-start because vaccination coverage was low, about 1000 people had already caught it by the time it was detected, and the outbreak had a springboard in the super-spreading church event in South Auckland.
"Finally, the outbreak got established among people who were living in marginalised sections of the community, including the homeless and those in transitional housing, as well as gangs, and this has made case identification and contact tracing very difficult," he said.
"New Zealand is paying the price for allowing such a big gap to develop, over several decades, between the rich and poor in our society. Infectious diseases typically spread most rapidly among the poor and marginalised, including people in crowded housing.
"These people suffer the most, but the whole community is worse off as well."
Prime Minister Jacinda Ardern has repeatedly said that there is no playbook for dealing with Covid-19, and Skegg had some sympathy, saying no one is every fully prepared for an epidemic.
"But our public health function, both centrally in the Ministry of Health and regionally in DHBs has been run down for years. We are paying the price for this neglect.
"The shortage of manpower and expertise probably explains why more was not done to prepare for the inevitable Delta outbreak."
The ministry has been repeatedly criticised by Government-commissioned independent reports for failing to boost contact-tracing capacity.
It claimed to have surge capacity to contact trace 1000 daily cases and 6000 daily contacts, but the system was under severe strain at the end of August when the daily case numbers peaked at 82.
Covid-19 Response Minister Chris Hipkins has said that daily cases in the current outbreak could peak somewhere between 200 and the "high hundreds".
Director general of health Ashley Bloomfield said last week that contact tracing was now less focused on casual contacts, and there was still capacity to trace the contacts of "hundreds" of cases a day.
The Government is increasing funding to public health units from $10 million a year to $15m a year by 2023/24, and creating a Public Health Agency.
The ministry has also been slammed for taking so long to make more use of PCR saliva testing and rapid antigen testing, both of which are still considered to be under-utilised.
Aucklanders were frustrated at having to wait up to 12 hours to get tested at the start of the outbreak, when the Government was imploring people to go to testing stations. Rako Science, which has capacity to process 10,000 saliva tests a day, asked the ministry if they could help, but they say their request went unanswered.
"New Zealand has been too slow to adopt new approaches to testing, and the contact-tracing capacity of public health units still needs further strengthening," Skegg said.
But he said it was speculative to say it was wrong to move Auckland from level 4 to 3, or to allow outdoor picnics when case numbers were trending up.
"I was not involved in these decisions, but I take comfort from the fact that public health professionals working on the outbreak in Auckland judged that the changes were sensible.
"They may have realised that the outbreak could not be extinguished, even with continuation of the most rigorous lockdown measures."
Skegg said it was inevitable that the virus would seed into the community once the borders started to re-open, and the current outbreak had moved that timeline forward.
But he disagreed with comments - made by British commentators as well as former PM Sir John Key - that New Zealand had been living in a "hermit kingdom".
"As one newspaper columnist wrote, far from being turned into a 'hermit kingdom', New Zealand has been – in comparison with most of the world – 'a passable imitation of Shangri-la'."
Skegg said the next year or two will be "extremely challenging", and he has previously noted the importance of ensuring particular groups aren't left with lower levels of vaccination coverage.
"Ideally the vaccination coverage in Māori and Pasifika populations should be higher than in the rest of the population."
But he said there were good arguments both for and against setting a particular target for Māori, which many health and science experts have called for but Ardern has rejected.
Instead alert level lockdowns will no longer be needed when 90 per cent of eligible people in every DHB is fully vaccinated, while a $120m package will target boosting vaccinations among Māori.
"I am optimistic that the new funding for Māori health providers will help to fuel rapid progress in the coming weeks," Skegg said.
He said the phased re-opening of the borders hasn't been delayed by the outbreak, but there were now some "complex issues to be worked through".
This week the Government will outline MIQ changes that have been brought forward by the Delta outbreak.
The risk profile in Auckland has changed, and with over 100 cases now isolating at home, it no longer makes sense to have fully vaccinated arrivals from overseas with a negative pre-departure test in MIQ rooms for 14 days.
He said New Zealand could continue to be world-leading in its response to this pandemic.
But the most we can hope for is a "new abnormal".
"My greatest fear is that our health system, after years of frugality, may not be able to cope with the large surge in demand that will be caused by Covid-19.
"That is why I would implore my fellow citizens to get vaccinated quickly, and to keep following the public health measures that are recommended."
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