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A testing queue on the Gold Coast (Photo: Chris Hyde/Getty Images; design by Tina Tiller)
A testing queue on the Gold Coast (Photo: Chris Hyde/Getty Images; design by Tina Tiller)

SocietyJanuary 28, 2022

What can New Zealand learn from Queensland’s omicron surge?

A testing queue on the Gold Coast (Photo: Chris Hyde/Getty Images; design by Tina Tiller)
A testing queue on the Gold Coast (Photo: Chris Hyde/Getty Images; design by Tina Tiller)

Overseas examples should be treated with caution. But the Australian state shares a lot of important characteristics with New Zealand, writes Toby Manhire.

Vaccination levels. Public health measures. Historic immunity. Testing strategies. Demographic differences. Weather. There are many factors – many more than those just listed – that should keep us on tip-toes when seeking to compare Covid impacts in one jurisdiction and another. That doesn’t mean that overseas examples aren’t useful, however, as we in Aotearoa brace for the omicron variant to curl steeply up the skate ramp here. Our nearest neighbour offers one experience that is more useful than most: the state of Queensland.

Why Queensland? A few things. First, the population is roughly the same. As of the middle of last year, the state was home to a smidge over 5.2 million, according to official estimates. New Zealand’s population as of September according to the equivalent estimate: a smidge over 5.1 million. Queensland covers vastly more territory, but like New Zealand, one big city dominates – Brisbane is home to an even bigger proportion of Queenslanders than Auckland is to New Zealanders. And there’s another important characteristic we share: for the vast part of the pandemic, until the end of last year, Queensland was pursuing an elimination strategy, built on the pillars of tight border controls both domestically and internationally and the targeted use of lockdowns.

“Yes, I think Queensland is a useful indicator,” New Zealand Covid modelling expert Michael Plank told me when I ran that past him. He cautioned that “we have slightly higher vaccination rates than them”, but reckoned the state (along with South Australia) provides a more useful comparison than the big states, New South Wales and Victoria, where the high delta numbers before omicron’s arrival “complicates things”.

So, with all those caveats in mind, here’s the story – so far – of omicron’s impact in Queensland.

State government data

Cases

On December 8 last year, Queensland identified its first omicron cases among recently arrived people in quarantine facilities. The following day the state’s health minister confirmed that the Queensland domestic border would fully reopen at 1am on December 13, saying, “While this will mean a rise in Covid-19 cases, Queensland’s high vaccination rate means we are well prepared”; and, “Very few places in the world have achieved this level of protection before a Covid wave arrives.” 

That wave did arrive. Since the initial outbreak in 2020, the state’s seven-day rolling average of new cases has invariably hovered in the low single figures. On December 18, it had jumped to 39. A week later, on Christmas Day, it was 289. On new year’s day, 2,198. As omicron swept the state, the seven-day rolling average of new cases had again increased by January 18 to 21,244. 

To look at it another way, on December 13, when the border opened, Queensland had recorded a total of 2,176 Covid cases across the pandemic. By yesterday, it stood at 369,897.

There is hope among some that Queensland case numbers have hit their peak. The number has fallen in recent days; yesterday saw 11,600 new cases reported – that may look a lot, but it’s half of a week earlier. The state’s chief health officer this week told media he believes Gold Coast is now past the highest point of its impact, while Brisbane is on the brink of its peak, with Cairns and the regions to follow.

Melbourne University epidemiologist Nancy Baxter urged caution, however, telling the ABC: “Instead of a sharp curve it may actually be a lot longer … and there will be a plateau. Certainly going back to school will put additional pressure on, as will everyone coming back from holiday and getting back to work. That is going to drive more transmissions — we are not going to have another peak, but it may slow down the curve.”

Testing

Those case numbers are undoubtedly an undercount of the total number of infections. As across Australia and much of the world, the shortage of rapid antigen tests and the prevalence of mild or asymptomatic infection mean, as the state’s chief health officer has acknowledged, “Some people have had RATs that they’ve done at their own home and some people have been having difficulty getting a test.”

On January 2, the state premier said 18 million tests had been secured “to be provided free from public testing sites to people classified as close contacts”.

Deaths and hospitalisations 

Yesterday also brought the news that 15 more people with Covid had died, bringing the total deaths to 153. The vast majority of those – 139 lives – took place in the latest outbreak. Rest homes have proved especially vulnerable. More than 50 of the recent deaths were among aged care facility residents

As of yesterday there were 829 people in hospital in the state, with 48 of those in intensive care wards. While it’s important to remember there is a lag between case reports and hospitalisations, were it not for vaccinations and were they facing an earlier variant of the coronavirus, those case numbers would translate into dramatically higher hospitalisation and death tallies.

A queue for Covid-19 vaccination at a Brisbane Bunnings store in October 2021 (Photo: Dan Peled/Getty Images)

Pressure on the health system

It is difficult to compare hospital capacity, and in both Queensland and New Zealand, governments insist they have surge capacity for, respectively, 576 and 550 staffed ICU beds. Those numbers are, however, both debatable and a crude measure of hospitals’ and wider health services’ ability to manage the load.

The “staggered peaks” across the state’s population centres may help a strained health system cope. State premier Annastacia Palaszczuk this week said she was “very comfortable with the projections at the moment that we have bed capacity” and that the current “track is not as high for the demand of beds as we initially were expecting”. She added: “The fact that our hospitals are going to be reaching those peaks at different times should give Queenslanders a bit more comfort.”

In the Gold Coast, eight wards have been filled with Covid patients. But the pressure is immense. The medical director of infectious diseases for the Gold Coast, Kylie Alcorn, told the ABC: “We’re not sure that we’re at our peak, hopefully we are, but we’re very cautious about that and also even if we have reached our peak we expect the tail to be very long.” They had hoped to only need to devote “three or four” wards to Covid, but had prepared for the possibility of much worse scenarios. “We had [planned] for many, many more wards to an extra hospital, a makeshift hospital, if it became quite severe,” she said.

She said staff faced a “tiring time” but had so far been coping well.

Prevention measures

On December 18, new mask mandates came into force, requiring face coverings to be used on public transport, in indoor retail and other settings. 

Gathering restrictions are looser than New Zealand’s red light settings. There is no limit on group sizes in public outdoor spaces and gatherings at a private residence are limited to a maximum of 100 people, irrespective of vaccination status. There is no limit on numbers for businesses or hospitality venues where those attending can prove vaccination status.

As of January 22, fully vaccinated arrivals from overseas are no longer required to quarantine as long as they isolate on arrival until they receive a negative test. Before Christmas, the isolation requirement for close contacts of cases was halved from 14 to seven days.

Vaccination

As well as the tighter measures in New Zealand, we have an advantage on vaccination uptake. Here, 93.1% of people 12 and over have had two doses; in Queensland that number is 88%. As we’re often, rightly, reminded, the research clearly shows the battle against omicron is bolstered substantially by a booster. On that count, we’re about even, with both jurisdictions running a little over 30% for people 18 and over. 

The Queensland experience has been less frightening than that in New South Wales and Victoria, where the health system has been pushed to crisis point. Why? According to infectious diseases expert Paul Griffith, it’s down to a combination of factors, including high vaccine uptake, a less congested urban population, ventilation, and public compliance with health orders. That came with an important reminder, however. “We have to remember that just because we pass the peak, doesn’t mean that transmission stops occurring … It’ll decline at approximately the same rate that it has increased and we’re not going to go back to zero. Potentially another variant will be introduced to our population at some point in the future and we are going to have to continue to make sure we have some basic strategies in place and we don’t get too complacent.”

To repeat: overseas examples are useful indications, but absolutely not templates. The Queensland experience does, however, help us get to grips with the vertiginous growth we’re about to encounter, as well as offering hope that some of the higher projections, such as that “50k daily cases by Waitangi Day” headline, will prove to be substantially overstated. 

Keep going!
Image: Tina Tiller
Image: Tina Tiller

SocietyJanuary 27, 2022

Will we really see 50,000 daily omicron infections by Waitangi weekend?

Image: Tina Tiller
Image: Tina Tiller

A projection of tens of thousands of infections by the first week of February made headlines this morning. Was it realistic? Auckland University statistician Thomas Lumley digs into the modelling.

This morning a headline on RNZ read ‘Omicron: Modelling suggests NZ could face peak of 80,000 daily infections’. The report, based on modelling by the US-based Institute for Health Metrics and Evaluation (IHME) began: “New Zealand could be facing 50,000 daily Omicron infections by Waitangi weekend”. This is technically correct, but in this context that is not the best kind of correct.

First, this is a model for infections, not cases. It includes asymptomatic infections (which are definitely a thing) and infections that just don’t get reported. The modelled peak for cases is a couple of weeks later, and about a factor of 7 lower.  So 50,000 daily infections by Waitangi weekend, peaking at 80,000 a few weeks later means 425 daily cases by Waitangi weekend, peaking around 11,000 daily cases by late March, if we believe the model. Given that we have been seeing reporting of cases, not infections, for the past two years, it’s misleading to quote a number that’s twice as soon and an order of magnitude higher.

Is it realistic that so many cases get unreported? It’s not clear. The best data on this, according to Trevor Bedford, who knows his Covid, is from the UK, where they have a mail-out prevalence survey. He estimates that the UK reports about three in 10 cases, and thinks it would be a bit lower for the US. I’d be surprised if it’s lower than the UK here, at least for the next few weeks. So, that conflicts a bit with the IHME infections model.

So, is the model right? Well, on the one hand, it’s a serious effort at modelling and should be taken seriously. On the other hand, it’s a model for everywhere in the world, so the amount of attention given to New Zealand data and outcomes will be quite limited. NZ-based modellers put rather more effort into modelling New Zealand data and New Zealand policies.

The reasons that New Zealand eventually controlled our delta outbreak were specific to New Zealand: lots of new vaccinations, quite good adherence to interventions, being happy to take it outside, being on a small island in the tropics, whatever. This sort of thing is hard for a worldwide model to pick up. As RNZ says, the model has a prediction if we use masks, and a prediction if everyone gets boosted; these are lower. It doesn’t have a prediction that accounts for capacity restrictions or vaccination of children. It’s a model where “flattening the curve” fails completely.

Looking at the model in more detail, it does seem that there are some issues with the NZ data feeds to the IMHE model. The model for testing looks like this:

That’s clearly wrong in two ways: first, it’s not going to be steady like that. More importantly, it’s too low by about a factor of 50. Here’s what the Ministry of Health says daily testing data looks like:

The IMHE vaccination model is also somewhat out of date:

It projects vaccinations as stopping in mid-November. They didn’t.

What can we say about the projections? Well, Victoria, with a slightly higher population, somewhat weaker restrictions, and not wildly different vaccination rate peaked at about 14,000 cases per day. So that’s clearly in the plausible range, and would be bad enough. It’s not out of the question that things get as bad as the IHME estimate, but I think it’s unrealistic to think of it as a most likely projection. And it certainly doesn’t need the confusion of “infections” with “cases”.

This article was first published on StatsChat, the University of Auckland statistics department blog.

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