COVID-19 modelling reports

From the Ministry of Health:

These modelling reports were commissioned by the Ministry to help us understand the health outcomes and impacts on New Zealand of COVID-19 and to inform the response strategy.

The reports have been completed by Wellington researchers from the University of Otago in collaboration with university colleagues from Germany. The models have been revised based on feedback from peer reviewers, the Ministry of Health’s Chief Science Advisor and public health officials.

Modelling will help inform Government decisions on when, how much, and for how-long, the country can ease the lockdown and other measures.

It’s critical to understand that each of the models presents a number of potential future scenarios; there are no “predictions”.

Each model has its own degree of uncertainty determined by the assumptions required for any modelling work, and those assumptions are based on the best information available from overseas evidence.



Successful lockdown could buy enough time for a vaccine

But that sounds like a lockdown far longer than 4 weeks, although a month could be sufficient if all measures are rigidly followed and enforced.

Te Pūnaha Matatini, the centre for research excellence that Shaun Hendy leads, studies complex systems and networks. Right now, he and the centre’s other researchers are working to predict how Covid-19’s web of infection might spread – and if it’s possible to slow it down or even stop it.

Modelling shows NZ’s lockdown could buy time for a vaccine:

Modelling done by New Zealand researchers shows the lockdown measures now in place could buy the country more than a year for a vaccine or treatment to be developed.

However, the research shows that without a vaccine or cure, cases of Covid-19 will still peak well beyond hospital capacity as soon as any lockdown ends.

The modelling, released today by Te Punaha Matatini, shows measures similar to those now in place can suppress the virus for up to 400 days but infections could spike as soon as they are gone, because the population will not have developed any herd immunity.

However, any fewer restrictions would result in a peak of at least six times hospital capacity within just a few months.

The paper compares a “suppression strategy” – a sustained period of restrictions – with a “mitigation strategy”, where controls are lifted for brief periods before being put in place again as infections rise and ICU beds fill up.

In all scenarios, the lockdown period is modelled to last significantly longer than the initial four weeks that began today.

However, one of the researchers, University of Auckland Professor Shaun Hendy, told RNZ the current lockdown could be sufficient if all measures were rigidly enforced.

“Provided the contact tracing, testing, and containment strategy works then we may be able to relax in four weeks. But we need to cut cases to just a handful.”

The researchers wrote that both strategies were “fraught with uncertainty” but suppression at least had the advantage of buying New Zealand time until a vaccine or treatment became available.

“The initial modelling the team published yesterday is stark and, frankly, terrifying”:

Left unchecked, the virus would eventually infect 89 percent of New Zealand’s population and kill up to 80,000 people in a worst-case scenario.

ICU beds would reach capacity within two months and the number of patients needing intensive care would exceed 10 times that capacity by the time the virus peaked.

“Tens of thousands of people would die, our health system would collapse and people wouldn’t be able to get proper treatment. That explains why the government’s been prepared to take such drastic steps,” Hendy says. “The worst-case scenario is a really unpalatable one.”

Even the best-case scenario is hard to swallow. It assumes restrictions similar to the lockdown now in place – but suggests that unless testing, contact tracing, and isolation cut the number of cases to just a handful, the restrictions might need to remain in place for over a year.

And if the cases can’t be stamped out under those restrictions, the eventual peak will swell well beyond hospital capacity as soon as any lockdown ends, unless a vaccine or treatment is found in the interim.

“When controls are lifted after 400 days, an outbreak occurs with a similar peak size as for an uncontrolled epidemic,” Hendy and his colleagues wrote in a paper rushed out yesterday. “In other words, these strategies can delay but not prevent the epidemic.”

The good news – if there is any – is that while strict suppression measures remain in place, fatalities should remain in the low dozens and hospital capacity wouldn’t be exceeded. That would buy New Zealand time to wait for a vaccine or a successful treatment.

A lot of guesswork but also a lot of cause for concern.