A scientist whose work helped the Government decide when to lift lockdown levels has criticised a report which suggested lengthening the time spent in level 4 cost a fortune, while providing few health benefits.
Late in April, Prime Minister Jacinda Ardern announced the country would spend an extra five days at alert level 4 - the strictest in the Government's pandemic response - than originally planned.
Director-General of Health Ashley Bloomfield at the time said the goal was to "maximise" the gains achieved under four weeks of level 4, which saw daily COVID-19 infection numbers drop from 89 to single-digits.
The Productivity Commission, after discussing the impact of the extension with Treasury officials, subsequently commissioned a report, which was completed on May 2.
What the report said
The report, released to Newshub under the Official Information Act, looked at three potential scenarios under the reduced restrictions of alert level 3:
- COVID-19 transmission would keep declining, with its reproduction number (R0) below one - meaning each infected person, on average passed it to fewer than one other
- the virus' R0 number rising above one, meaning exponential growth in cases, possibly undetected
- or an R0 of exactly one.
The analysis found little difference in health outcomes between extending the lockdown five days and going to level three as originally scheduled, if the R0 number was above or below one.
If the R0 was above one "it would only delay, not prevent, a return to level 4", the report said. The five extra days spent under level 4 would only avoid 96 new cases and one death, saving just eight quality-adjusted life years (QALYs). If it was below one - as turned out to be the case - the report said only 159 cases and two deaths would have been avoided, and 14 QALYs saved.
'Quality-adjusted' refers to the "quality of life during the period lived, relative to that of an 'average' healthy person of the same sex and age," according to the report.
At an R0 of one - the least likely scenario - 2738 infections and 30 deaths would have been avoided, the report concluded. Even then, because most of the dead would likely be elderly, the number of QALYs saved would have been only 239.
The economic cost of the five-day extension either way was $741 million, the report concluded - equivalent to losing 22,453 QALYs, "using Treasury's $33,000 figure for the value of a QALY".
The report's author said the analysis excluded "incidental health benefits of the lockdown" like the reduced number of road deaths, accidents and sports injuries during lockdown.
"Such health benefits, however, are not costless. People value their freedom to travel, play sport and take part in other activities that come with a higher risk of personal injury. Under normal circumstances, society accepts that these activities should be allowed - implicitly assuming they have a net benefit."
Overall, the report concluded "that straight to level 3 outperforms an extra five days at level 4 on all criteria considered".
Coming two weeks after the Government made its call to extend the level 4 lockdown, the report was not used as part of the decision-making process. Treasury told Newhsub it was "intended to demonstrate a technique with a concrete example, not to critique the Government's decision".
Shaun Hendy of research group Te Pūnaha Matatini helped with modelling the Government did use to make its decisions. At the time, he was pushing for a two-week extension, saying this would give New Zealand a 50 percent chance of elimination. According to his modelling, a five-day extension took the probability of elimination to just 14 percent.
Te Pūnaha Matatini's modelling in early April said it would be "optimistic" to assume community transmission could be wiped out in just 28 days of level 4 restrictions.
Dr Hendy told Newshub the Productivity Commission's modelling was severely flawed because it didn't take into account the possibility of a second wave - which would be not just a disaster from a health perspective, but economically.
"Because it ignores the possibility of a Victoria-style secondary outbreak, you basically can't use it to inform your decision-making."
After taming the initial outbreak without implementing a full lockdown, Australia's state of Victoria has been plunged into the equivalent of New Zealand's alert level 4.
While an "interesting piece of work", Dr Hendy said ultimately it was a "toy model" which "grossly underestimated" the benefits of staying in level 4.
"What they didn't seem to realise is that once case numbers become low - under 10 - the probability of elimination starts to become significant. Most people don't pass COVID-19 onto anyone, while a few people pass it on to large numbers - once you have a handful of cases there is a chance the disease will simply fade out, particularly while in a level 4-style lockdown."
He said Te Pūnaha Matatini reached out to the Productivity Commission at the time to help out, but was turned away.
"It wasn't necessarily apparent to everyone back when we were in lockdown.... but those of use who were doing it at the time, making the calculations at the time, were aware of the possibility of a second wave... that's why we recommended that extension."
The author of the report was not available to talk about it. A Productivity Commission spokesperson told Newshub it was a "technical piece, aimed mostly to explore the methodological issues in this sort of analysis".
"The conclusion reached with this methodology [was] that it would be extremely unlikely that the extra five days of lockdown would be sufficient to make a difference between elimination, or failure to eliminate. It would change the starting point and therefore the timing of achieving elimination, and that has consequences which are identified.
"At that decision point, Shaun was arguing that an extra 14 days would be necessary to lock in elimination, although we are unsure of the basis for his contention.
"Of course, reasonable people can come to different judgements and plug in different assumptions. But the paper was developed to allow those different assumptions and judgements to be explored in a clear and explicit manner."
In the months since the report was written, New Zealand has gone to alert level 1 - effectively back to normal for most, but with restrictions at the border. It's been more than three months since the last case of community transmission.
Unemployment hasn't risen as much as many predicted, though it's expected to get worse over the next couple of months as the Government's wage subsidy scheme expires.
GDP shrank by 1.6 percent in the March quarter. The figures for the three months to June are expected to be released next month.
Dr Bloomfield this week warned it was likely a matter of when, not if, there is a second wave of the pandemic here, based on what's happened overseas in recent months.