A tougher 4-week lockdown could save Sydney months of stay-at-home orders, our modelling shows

Allan Saul, Burnet Institute; Margaret Hellard, Burnet Institute; Michael Toole, Burnet Institute; Nick Scott, Burnet Institute, and Romesh Abeysuriya, Burnet InstituteResidents in Sydney, the NSW Central Coast, Blue Mountains and Wollongong today received confirmation their lockdown would be extended to at least 30 July.

But our modelling suggests it may take until the end of the year to get case numbers close to zero, unless more stringent measures are introduced.

NSW health authorities increased restrictions on Friday. These limit outdoor gatherings to two people, exercise to within 10km from your home, and shopping to one person from a household each day, with no browsing.

These restrictions are similar to Victoria’s Stage 3 and came on top of existing rules, which began on June 23, to only leave your home for four reasons: work/education, care/compassion, shopping for essential supplies, and exercise.

But additional measures – at least as strong as in Melbourne’s Stage 4 – are needed to get the greater Sydney outbreak under control.

For Melbourne’s second wave, this included closing non-essential retail, restricting movements to 5km from home and within the hours of 8pm to 5am, and mask-wearing outdoors.

COVID case numbers will fall if Victorian Stage 4 measures are applied in greater Sydney, for at least a month.

Our predictions

Our modelling shows that without the initial stay-at-home orders, the results would have been catastrophic (red line).

NSW’s updated level of restrictions (orange line, similar to Victoria’s Stage 3 + masks) would prevent daily case numbers from increasing further. But it’s not enough to eliminate community transmission before the end of the year.

But if Stage 4 restrictions were applied now (blue line), the epidemic curve would decline sharply.

It’s difficult to estimate the time to return case numbers from current levels to a seven-day average of less than five per day, but it’s likely to take at least a month.

So how did we reach these conclusions? We use two complementary modelling approaches to generate information about the measures needed to get case numbers under control.

Simulating people’s decisions

The first model, COVASIM, simulates individual people who reflect the diversity of the population. Individuals are allocated different numbers of daily contacts and can participate in various activities (for example going to school, work, bars/cafes, shopping, playing sport), which affect their risk of transmission.

People respond differently to COVID-19: whether they get tested, how long they wait before being tested, and how compliant they are with quarantine. For infected people, their infectiousness and disease prognoses also depend on their age and vaccine status.

COVASIM includes interventions such as testing, contact tracing and quarantine, and public health restrictions that can reduce transmission risk, such as masks and density limits, or the number of contacts.

We calibrated this model using extensive data from Melbourne’s second wave, then simulated a theoretical Delta variant outbreak. We wanted to know whether previous restrictions would be likely to contain the Delta variant, given improved contact tracing and limited vaccine coverage.

To produce a “Sydney-sized” outbreak, we ran the model with light restrictions until it reached a seven-day average of 30 diagnoses a day. We then applied three policy packages: no additional restrictions, restrictions similar to Melbourne’s Stage 3 + masks, and Stage 4 restrictions.

Looking at the whole city

Our second model, MACROMOD, takes the opposite view to COVASIM: it models what happens at the city level, instead of building up from the outcomes of many individual behaviours.

It assumes the epidemic proceeds as a series of periods of exponential growth or decline and is being updated daily as new daily case data becomes available.

MACROMOD was successful in describing Melbourne’s second wave (June to November 2020) and accurately predicted the time to reach zero cases in Melbourne under Stage 4 restrictions.

What does it predict for Sydney?

We modelled Sydney’s current outbreak with MACROMOD for 21 days from June 23, when stay-at-home orders began, to July 13.

The impact of the stay-at-home orders was expected to start by July 1. But we couldn’t detect any decrease in the exponential growth in COVID case numbers.

This tells us that despite the fine work done by contact tracers and the NSW public, the high transmissibility of the Delta variant requires a much more vigorous response.

We then projected the model forward to predict the impact of the extended controls on July 9, and a further hypothetical increase similar to Melbourne’s Stage 4 restrictions.

The model suggests that the extended controls may be enough to “flatten the curve”, but are unlikely to contain the outbreak.

Thankfully NSW still has public health levers it could use to get the outbreak under control. We found if Stage 4 restrictions were applied now, the epidemic curve would decline sharply.

Read more:
80% vaccination won’t get us herd immunity, but it could mean safely opening international borders

The Conversation

Allan Saul, Senior Principal Research Fellow (Honorary), Burnet Institute; Margaret Hellard, Deputy Director (Programs), Burnet Institute; Michael Toole, Professor of International Health, Burnet Institute; Nick Scott, Econometrician, Burnet Institute, and Romesh Abeysuriya, Senior Research Officer – Computational Epidemic Modelling, Burnet Institute

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Support package for Sydney better and more fit for purpose than JobKeeper

Steven Hamilton, Crawford School of Public Policy, Australian National UniversityThe economic support package announced by Prime Minister Scott Morrison and NSW Premier Gladys Berejiklian is exactly what is needed, and just in the nick of time.

In a number of ways, in fact, it is more fit for purpose than the JobKeeper and JobSeeker policies that played such a key role in shielding the nation from the worst economic impacts of the COVID-19 pandemic.

There is support for workers who lose their jobs or have their hours cut, and incentives for affected businesses to keep their workers on the payroll.

In the face of what looks set to be an extended lockdown for Sydney, significant support was clearly needed. The federal government has rightly resisted calls to reinstate the JobKeeper wage subsidy, and opted instead for a new, more flexible scheme better suited to the circumstances.

There are two key planks of support, working together.

Read more:
Yes, lockdowns are costly. But the alternatives are worse

Payments to individuals

The first is payments for individuals. For Melbourne’s lockdown in late May and early June the federal government provided up to A$500 a week to those losing more than 20 hours of work a week. It is boosting this to $600 a week. For those losing eight to 20 hours a week, the payment is increasing from $325 to $375. The liquid assets test that applied to the Victorian payments has been scrapped.

Critically, any worker who loses enough hours is eligible. That means the payment can help virtually all workers losing work due to the lockdown, at least to some degree, and gives businesses the flexibility to scale down by reducing hours while minimising the impact on workers. We can squabble about the generosity of the payment, but it is more than double the rate of JobSeeker.

Importantly, it means the cost of the lockdown is being shared by the federal and state governments, rather than just falling on businesses and workers. This provides confidence that lockdown decisions will be made entirely in accordance with the public health advice.

Payments to businesses

The second plank is a partnership between the federal and state governments to revive the cash-flow boost instituted at the beginning of the pandemic, before the federal government introduced JobKeeper.

Only businesses with annual turnover between $75,000 and $50 million are eligible. For those suffering a 30% decline in annual turnover (compared to pre-pandemic times), the payment will cover 40% of their payroll costs up to a maximum of $10,000 a week. To qualify, however, they must not lay off any staff.

This emulates one of the best features of JobKeeper by maintaining the connection between employers and employees through the crisis to speed the recovery once restrictions lift.

Read more:
Why most economists continue to back lockdowns

Improvements on JobKeeper

In his press conference, the Prime Minister described the measures as targeted, timely, proportionate, scalable and able to be administered quickly and simply.

It’s hard to disagree.

One aspect that’s a big improvement over JobKeeper is that the turnover test is based on actual turnover, rather than projected turnover or trailing turnover, as with the earlier schemes. This should see the money better targeted to the businesses genuinely in need.

Another improvement is that it drops the cumbersome JobKeeper approach of paying employers a per-employee subsidy they were then expected to pass on to each worker at a fixed rate regardless of actual hours. This time businesses will get a payroll subsidy they can use however they see fit — so long as they don’t lay anyone off.

This should maximise flexibility, and minimise business failures and layoffs. And compliance should be straightforward to enforce via Business Activity Statements and Single Touch Payroll records.

But it is all a bit reactive

I do, however, see one negative.

Just as many ordinary Australians seem to have assumed and behaved as though the pandemic was behind us, so did the federal government in configuring its fiscal support measures earlier this year.

It was right to end the JobSeeker supplement and JobKeeper as the economy recovered. But it was wrong not to replace them with a suite of more flexible, contingent measures to be triggered in the event of future lockdowns. It should have foreseen the possibility of a future prolonged lockdown and been prepared for it, rather than be forced to play catch-up.

Following the announcement of these measures, the federal minister for government services, Linda Reynolds, said “our response will continue to evolve”. But what businesses and consumers have needed all along is certainty — to know that if things go pear-shaped there’s a plan and they will be looked after.

Without that certainty, consumers will hold back on spending and businesses will hold back on investment, putting a brake on the economic recovery.

Every Australian consumer, worker and business — in every Australian state and territory — needs to know today exactly how they’ll be supported should things get a lot worse or go on a lot longer than currently expected.The Conversation

Steven Hamilton, Visiting Fellow, Tax and Transfer Policy Institute, Crawford School of Public Policy, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Why the federal government’s COVID-19 fear appeal to Sydney residents won’t work

Australian Government

Jane Speight, Deakin UniversityOn Sunday July 11, the federal government released two new COVID-19 campaigns.

The first, shared across Australia, is a call to “arm yourself” (and others) against the virus by getting vaccinated as soon as you’re eligible.

The second is a graphic fear appeal, broadcast only in New South Wales, which shows a young woman in a hospital bed struggling to breathe. The advert has the caption: “COVID-19 can affect anyone. Stay home. Get tested. Book your vaccination”.

It’s clearly intended to leave the NSW audience shaken by the severity of the virus, and with the knowledge that residents, particularly younger people, are susceptible to the virus.

It’s easy to see why fear-based campaigns are appealing. Some may even think focusing the public’s attention on the severity of COVID is necessary to combat complacency in the wake of the low number of deaths in Australia overall.

Unfortunately, a fear appeal about COVID, particularly in NSW at this point in time, is highly unlikely to be effective, and certainly not as effective as some other approaches could be.

Fear appeals can have unintended consequences

The underlying assumption of fear appeals is that, when people are confronted emotionally with the potential severity of a threat, they will act accordingly to prevent it. The reasoning is simple enough, but it’s only true when certain other conditions are met.

This COVID vaccine advert addresses motivation, but it ignores other key elements of behaviour change. That is, do people have the capability and opportunity to make the change(s)?

When one or both are absent, people are likely to react defensively. They tend to become more, not less, distressed, and this doesn’t necessarily translate to behaviour change.

Indeed, increasing fear may actually be unhelpful. Fear drives panic, stigma and further fears. It acts as a barrier to an effective community response.

Fear can discourage people from adopting protective behaviours, such as hand hygiene, physical distancing or self-isolation; from seeking health-care for screening or treatment; and from disclosing their illness, to avoid discrimination and/or abuse. There are also numerous accounts of people panic-buying in supermarkets.

Psychological theory and evidence do not support fear appeals overall.

Threatening communications are effective only when people have high “self-efficacy” to undertake the behaviours. This means the target audience needs to be confident they can actually change their behaviours.

Can people change their behaviour in this context?

When we examine the three behaviours the federal government promotes in this campaign, it’s clear that capability and opportunity are, at best, variable across the community.

Let’s take a look:

1. “Stay home”

People’s ability to stay home is based not only on their perception of threat, but also on their personal, economic and social circumstances.

For example, it has been evident during the pandemic that some people cannot or do not stay at home because they have insecure or low-paid work with no sick leave entitlements.

Read more:
‘Far too many’ Victorians are going to work while sick. Far too many have no choice

2. “Get tested”

When people know they have engaged in potentially risky behaviours, like shopping or visiting family and friends, they are likely to be anxious about what a COVID test will reveal. This can lead to avoidance of the test.

They may well also be concerned about the potential consequences beyond the threat to their health. They might wonder whether they will be punished with fines they cannot afford, or shamed by the media for their behaviour.

Read more:
10am brunch, 1pm Kmart: when the media pokes fun at someone’s lifestyle, it’s harder for the next person to get COVID tested

3. “Book your vaccination”

Australia’s problem with vaccine hesitancy is well-documented. But, we need strategies to encourage people to make the right decisions, not beat them into submission.

Especially so, given the federal government’s vaccine supply and rollout program, which is currently an international embarrassment. According to the latest figures, Australia has delivered 35 vaccine doses per 100 people. That compares to 126 in Israel, 118 in the UK, 99 in the USA, and 44 worldwide.

Read more:
Australia has not learned the lessons of its bungled COVID vaccine rollout

In many ways, this campaign is unethical

It’s also unethical to use distressing campaigns when many people, particularly younger people, are already experiencing considerable mental health impacts due to the pandemic. When many don’t have the financial security to stay at home. When they are genuinely confused by the risks associated with the vaccines, and many remain unable to access the vaccine. When the reality is the Australian health-care system has the capacity (currently) to ensure no-one would be left alone in hospital gasping for breath.

And when the NSW government itself has done a 180-degree turnaround in its messaging in a single day from: we may need to give up on lockdown and live with the Delta variant to NSW “can’t live reasonably” with the Delta variant — and now expects a similarly rapid U-turn from the public.

It’s not surprising young people (and many others) are already expressing their outrage at this government advert.

We need the government to leave behind the draconian fear appeals of the 1980s, and instead embrace the lessons learned about “gain-framing” from multiple, evidence-based mass communication campaigns.

Gain-framed messages focus on the positive consequences of adopting the behaviour rather than on the losses associated with not doing the behaviour.

Recent COVID vaccine campaigns in Europe have been uplifting. Some dare us to dream of a COVID-free future, for example one French campaign.

And some, like one UK campaign, even use a little humour.

At this point in the pandemic, we don’t need scare tactics. What we need is for everyone to feel encouraged, empowered and supported to do the right thing to protect their own health and that of the wider NSW and Australian community.

And we need governments to understand and use the theory and evidence supporting an effective approach.The Conversation

Jane Speight, Foundation Director, Australian Centre for Behavioural Research in Diabetes, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

As Sydney’s lockdown continues, what support is available — and needed — for people losing income?

Mick Tsikas/AAP

Peter Whiteford, Crawford School of Public Policy, Australian National University and Bruce Bradbury, UNSWGreater Sydney is in its third week of lockdown, with no clear end in sight. The situation calls for support both for businesses and households suffering severe income loss in the weeks ahead.

Greater Sydney makes up about one-fifth of the Australian population, so is a significant chunk of our economy and community.

It’s worth noting when the (now extinct) Coronavirus Supplement was announced on March 22 2020, there were 179 new cases per day for all of Australia. When the (also now extinct) JobKeeper Payment was announced a week later, there were 383 new cases per day.

There were 112 new cases announced in NSW alone on Monday.

A federal government responsibility

In June, Prime Minister Scott Morrison indicated business support was a state government responsibility. But income support for households is a federal government responsibility.

In 2020, the Morrison government showed great flexibility. JobKeeper supported employers to maintain part-wages for workers who would otherwise be stood down, and the Coronavirus Supplement gave additional support to those who lost their jobs.

Sign at Bondi Beach 'Stay at home orders for Greater Sydney'.
Sydney had been in lockdown since June 26.
Mick Tsikas/AAP

These programs went a long way towards addressing a weakness of Australia’s social security system — the lack of insurance against sudden income loss when workers are laid off (for whatever reason). Indeed, for a while, the Coronavirus Supplement also worked to address another major weakness, the below-poverty line income for the long-term unemployed.

JobKeeper and the Coronavirus Supplement ended earlier this year. Most recently, the federal government has built on existing schemes to assist people during natural disasters, to support those during lockdowns or quarantine.

The last few months in Melbourne and Sydney show the COVID crisis is far from finished. Morrison has flagged that further financial support is being considered by the government. Treasury is reportedly working on options.

There are currently two main forms of support.

The COVID-19 Disaster Payment

The first main support is the COVID-19 Disaster Payment. This kicks in once a lockdown has gone on for more than a week. For those losing under 20 hours work, the payment is $325 per week, and for those losing 20 hours or more of work, the payment is $500 per week.

Read more:
There’s a new temporary COVID disaster payment – who can get it? Who is missing out?

There are several eligibility criteria: recipients must be unable to attend work and have lost income, they can’t have access to appropriate paid leave and they can’t be receiving an income support payment, a state pandemic payment or the Pandemic Leave Disaster Payment for the same period.

Last week, Morrison announced the liquid assets limit of $10,000 would be waived from the third week of a lockdown.

Pandemic leave payment

The second key support is the Pandemic Leave Disaster Payment, where an appropriate local health authority has told people to self-isolate or quarantine, or for those who need to care for someone with COVID-19. This includes Australian residents and those with a working visa.

The payment is $1,500 for each 14-day period someone needs to self-isolate or quarantine. A new claim must be made each 14-day period and Services Australia has set up accelerated application processes.

As with the COVID disaster payment, those with any income from paid work or other leave entitlements, or on income support payments, are not eligible.

How adequate are these measures?

Whether support is adequate depends on the spread of the virus and its economic impact in coming weeks. But there are already gaps in support.

It is confusing to have two payments at different levels, with people required to quarantine receiving greater support than those locked down, even when financial losses may be similar.

A woman crosses a deserted street in the Sydney CBD.
The Delta variant has turned the Sydney CBD into a ghost town.
Mick Tsikas/AAP

The Pandemic Leave Disaster Payment is comparable to JobKeeper, but the Covid-19 Disaster Payment is considerably less (although higher than JobSeeker Payment for the unemployed).

As we have already noted, both payments have significant exclusions. With the COVID-19 payment, apart from being unavailable for the first week, people must submit a new claim for each additional week of lockdown.

What about those already on welfare?

While the government increased the base rate of JobSeeker Payment earlier this year, Australia still has the second lowest “replacement rate” (relative to wages) for the unemployed in all OECD countries.

Another significant gap is most of the current help cannot go to people already receiving income support, although many of them may lose income in lockdown.

Read more:
Unemployment support will be slashed by $300 this week. This won’t help people find work

Welfare recipients who have to go into isolation or quarantine can access a one-off crisis payment (equal to a week’s pay at the maximum basic rate of their payment), but this is only available twice in a six month period.

According to Australian government data, in May, nearly one in four people receiving Youth Allowance (Other) and more than 20% of those receiving JobSeeker had part-time earnings, which is crucial to help people paying rent and bills. If they lose earnings, their benefits will increase, but by less than half the earnings lost.

Business support

We keep hearing reports about how small business is suffering badly.

Small businesses have many fixed costs — most notably rent — that will not be supported. More generally, so far, most of the costs of the lockdowns have been borne by either employees, employers in locked down industries, or government.

But a wider sharing of the costs via rent and interest moratoriums for affected businesses and households should be considered. This requires co-ordinated action by the state and federal governments.

Importantly, state governments are looking at their own measures. Last week, Victoria announced it would trial up to five days of sick or carer’s leave, at minimum wage rates, to workers in high-risk industries, including aged care, cleaners, supermarket workers, hospitality workers and security guards. However, this will not start until early 2022.

NSW has been pushing the federal government to jointly devise a new scheme to save jobs. An announcement is expected imminently.

Whatever this is, governments need to be realistic about what businesses and households are facing. The longer lockdown lasts, the more people will need longer-term solutions to costs they can’t get away from, like mortages, rents and basic living expenses.The Conversation

Peter Whiteford, Professor, Crawford School of Public Policy, Australian National University and Bruce Bradbury, Associate Professor, Social Policy Research Centre, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Sydney is locked down for another 7 days. So what will it take to lift restrictions?

AAP/Dan Himbrechts

Hassan Vally, La Trobe University and Catherine Bennett, Deakin UniversityNew South Wales Premier Gladys Berejiklian today confirmed what Sydney was fearing: the city’s lockdown will be extended for another week.

With 27 locally acquired cases identified in the past 24 hours, this decision isn’t surprising.

Of some concern, seven of these people had been moving around in the community during part of their infectious period. Another seven appear to have been in the community for the whole of their infectious period.

These aren’t the numbers you want to be seeing when considering emerging out of a lockdown.

So what are health authorities looking for when when making decisions about relaxing restrictions?

The first key factor is whether the public health team is identifying the epidemiological links between cases.

The second is whether contact tracers are able to identify all potential cases and quarantine them before they’re infectious. This is clearly not yet the case in NSW.

Remind me, why did Sydney go into lockdown?

After health authorities identified the initial cluster, it looked like it could be brought under control. But then they discovered a new, significant chain of transmission.

While it could be traced back to the Bondi Junction cluster, there had been more than one generation of spread in the community. This included a seafood wholesaler in Marrickville, with transmissions going back a week before they caught it, and a flight crew member who travelled interstate while likely to be infectious.

It would take some days to identify, trace, isolate and test all contacts.

The second and equally important reason for lockdown was contact tracers weren’t able to keep up with all the cases, despite identifying this outbreak within the first generation of spread.

Read more:
Did Sydney’s lockdown come too late? Here’s why it’s not that simple

Contact tracers were finding the interval between exposure and becoming infectious could, in some cases, be as short as 24 to 48 hours.

They were concerned that known chains were still active and other significant chains of transmission were yet to be discovered. So they needed the extra level of transmission suppression that lockdown brings.

What’s happened since?

Fortunately, no other chains have been unearthed linked to large workplaces or complex setting. But the outbreak isn’t yet contained, so restrictions are still needed.

However, this could turn around quickly, as the number of new exposure sites diminishes.

An important element of the public health response has been the decision to ask the households of those who have been to key exposure sites to also isolate while the infection status of the person exposed is worked out.

This, along with people rapidly self-identifying when new exposure sites are listed or older sites are reclassified to “close cotact” status, will allow the contact tracers to get ahead of the virus. Then, new cases will only be found in quarantine.

At that point, new cases may continue to be reported, but lockdown will no longer be necessary.

So what needs to happen for Sydney to end lockdown?

When it comes to relaxing restrictions in Sydney next week, there is a lot to consider.

First, we have to take into account we’re dealing with the more infectious Delta variant. It’s around twice as infectious as the original strain that emerged from Wuhan. This has considerably changed the risk assessment, given the ease and speed at which it seems to spread from one person to another.

Read more:
Why is Delta such a worry? It’s more infectious, probably causes more severe disease, and challenges our vaccines

It’s also important to consider we’ve seen casual exposures in shared public indoor places contribute more to the spread in this outbreak. Indeed, this outbreak was seeded with a number of casual exposures resulting in new cases and widespread transmission within the first generation of spread.

Schools have become key transmission sites in this outbreak, and also in the smaller Delta outbreak in Melbourne in May. So, while schools were once seen as less worrisome locations, they’re now a more important consideration.

So far, the NSW government has delayed the return of students, with those in greater Sydney moving to home learning next week. The premier said this wasn’t because they were risky places, but to “stop literally hundreds of thousands of adults moving around and interacting with each other” at pick up and drop off times.

Hopefully the extra week of lockdown and home learning is enough to stamp out transmission, so NSW can start to get back to where it was a few weeks ago.

As Berejiklian said today, there is only one thing worse than a lockdown and that is cycling in and out of lockdowns, given the huge economic and social costs.

All the evidence shows that going hard to suppress transmission pays dividends many times over for both health and economic outcomes.

And of course, as soon as we reach a high enough level of vaccine coverage, lockdowns will be a thing of the past. This should be a big motivation for all of us to get vaccinated.

Read more:
Australia has a new four-phase plan for a return to normality. Here’s what we know so far

The Conversation

Hassan Vally, Associate Professor, La Trobe University and Catherine Bennett, Chair in Epidemiology, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Did Sydney’s lockdown come too late? Here’s why it’s not that simple

Mick Tsikas/AAP

Catherine Bennett, Deakin UniversityLast Saturday, the New South Wales government announced a two-week lockdown for Greater Sydney, the Blue Mountains, Central Coast and Wollongong after a spike in new COVID cases.

It’s spawned a lot of commentary about whether NSW delayed going into lockdown, and therefore has caused itself a longer lockdown. Indeed, one modelling study by University of Sydney researchers, published last November, estimated delaying lockdown by three days would extend the lockdown by three weeks.

But it’s not that simple.

This kind of modelling is about using lockdown as a primary intervention where you’re relying on the lockdown itself to snuff out transmission. Even if the cases aren’t tested and recognised, the virus eventually runs out of new susceptible people to infect. This isn’t the case in NSW, which is still relying on a strategy of test, trace and isolate.

If this lockdown is about buying time to allow contact tracers to get in front of the virus by getting all at-risk contacts of cases in quarantine before they’re infectious, then a day’s “delay” is probably not going to add weeks to it. The modelling doesn’t apply in this scenario.

Whenever we’re evaluating a lockdown, there’s always an element of “hindsight being 20/20”. Some of the circuit-breaker lockdowns we’ve had over the past year didn’t change the management of cases and contacts because all community transmission that did occur after lockdown was among known contacts already in quarantine. But we didn’t know that until after the lockdown was called. Circuit-breakers are essentially insurance policies or safety nets (though we should still evaluate them to know when they are justified).

During this pandemic we’re often making decisions in situations of considerable uncertainty.

Things have clearly shifted in our latest outbreaks in Victoria and NSW. Contact tracers have been very effective at finding, linking and documenting the spread of cases. And in NSW’s latest outbreak, health authorities have had the added advantage of discovering the cluster within the first generations of spread. This means they’ve been able to collect data on where the virus was, and how transmission was occurring, in almost real time.

It’s easy to sit here and say locking down earlier would have made a difference. But when should it have been called? When we knew of only ten cases the Saturday before last? While infections among casual contacts were concerning, nobody knew 24 future cases would soon be exposed to a case at private party of 30 held later that same night.

So what works best in situations like this — go early just in case? I would argue go with the data when you are this close to the leading edge of the outbreak. Assess the data in real time and be prepared for a rapid change in response.

The emerging story over last week was of many cases, but almost all linked to the known cluster. By week’s end, it was clear at least one branch of the outbreak was missed with multiple cases infectious in the community over five days or more.

What led to this lockdown?

Rather than relying on high-level modelling of transmission risk and projections, we can also build a detailed picture of the epidemiology of an outbreak as it is playing out.

NSW has had very detailed transmission data on almost all cases, bar a handful, which puts them in a strong position.

A potential risk in relying on contact tracing is how quickly things can escalate if you miss a major chain of infection. This was the case for the cluster involving a seafood wholesaler in Marrickville, which was spreading invisibly and had transmissions going back a week before they caught it. On Sunday, ten of the 30 new cases announced were linked to this cluster.

Another factor was casual transmission. This Delta variant is much more infectious than previous strains, and some of the early cases in this outbreak occurred from merely “fleeting” exposure. Some of these early transmissions happened in places where health authorities couldn’t be confident they could track down all casual contacts, and those who were exposed may have underestimated their risk of having been infected.

Read more:
We’re seeing more casual COVID transmission. But is that because of the variant or better case tracking?

Yes it’s true almost all the cases are “linked” to previously known cases, but some of these were linked via a convoluted, longer path as a contact of earlier missed cases. This meant more people circulating while infectious over a larger number of days.

The distribution of cases also played a role. Even though it seems to still be largely focused around Bondi, cases and potential exposures were now spread beyond.

Should NSW have locked down a few days earlier? It’s hard to say, but will be important to evaluate when things settle

A lot of people forget there were only ten cases in total in this outbreak just over a week ago. There were two new cases per day between June 16 and 20 inclusive, which are numbers we all know are manageable for NSW contact tracers.

Should they have gone into a full lockdown on Sunday, June 20, when they had a total of ten cases? I don’t think you could defend that epidemiologically.

Cumulative cases then went from ten to 25 two days later, to 54 another two days later on June 24, to 112 on Saturday June 26 when lockdown was announced.

It looked like they were right on top of it, and were very close to getting to all contacts before their infectious periods. But they were still probably a day or so behind the virus. Even one infectious day each in the community by a few contacts simultaneously is very risky and adds to exposure sites.

This Delta variant also seems to have reduced the time between cases being exposed to the virus and becoming infectious themselves, according to NSW Chief Health Officer Kerry Chant.

All this painted a very different picture to the week before, and would have contributed to the decision to lock down.

We need to analyse the data

Now we need to evaluate this outbreak response, along with all others in Australia, and learn more about how the virus moves through our communities, our weak points, our most effective containment measures, and the optimal timing of these.

The lockdown won’t yet have played a significant role for new cases. But we also know from the timing of cases that locking down a few days earlier wouldn’t have stopped the seafood wholesaler outbreak, nor would it stop spread in high-risk essential workplaces.

Analysing the outbreak aims to understand any additional cases that might have been prevented with earlier lockdown, or how many cases will be prevented with lockdown in place now. It will allow us to, under various alternate scenarios, use these rich detailed case data to remove some of the uncertainty next time.The Conversation

Catherine Bennett, Chair in Epidemiology, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.