Michelle Grattan, University of CanberraPfizer doses in NSW will be spaced out to enable more first jabs to be administered quickly, as the Berejiklian government on Friday declared the Sydney COVID crisis a “national emergency”.
But the plea by the state for Pfizer doses to be diverted to Sydney as part of a refocusing of the national vaccine program has fallen on deaf ears.
Scott Morrison indicated if any extra Pfizer supplies became available they would be directed to NSW – but he made clear there would be no change in the national vaccination program.
“Where there is a potential to put more vaccines into NSW, even beyond what we’re already doing, well, of course, we will seek to do that. But we are not going to disrupt the vaccination program around the rest of the country,” he said after a meeting of the national cabinet.
Vaccines are distributed on a population basis, although NSW was recently given a special allocation of 300,000 doses, half AstraZeneca and half Pfizer.
Morrison also said suppression was the key immediate means of stopping community transmission and getting on top of the outbreak that is concentrated in south western Sydney. “Suppression is the primary tool to achieve that, and vaccines can help that.”
Earlier, General JJ Frewen, who is in charge of the vaccine rollout, was dismissive of the suggestion supplies be diverted.
“Vaccines are only one part of a response to the outbreak like this,” Frewen told a Senate committee.
Other states made it clear they would not give up any of their Pfizer supplies.
Morrison said extending the time between Pfizer doses – normally three weeks – to six weeks was within the advice of The Australian Technical Advisory Group on Immunisation (ATAGI). This would be done in NSW vaccination clinics.
He also said there was “agreement amongst the national cabinet that we need to continue to lean in to AstraZeneca, particularly in NSW”.
Australian Medical Association President Dr Omar Khorshid on Friday called on ATAGI to review its advice on AstraZeneca in response to the growing risks posed by the outbreak of the Delta variant in NSW.
“As we don’t have enough Pfizer to use in a targeted rollout, the only option is AstraZeneca. It will save lives and help see life return to some normality in Greater Sydney,” Khorshid said.
ATAGI has preferred Pfizer for those under 60, although it recently qualified its advice in light of the Sydney outbreak.
As NSW on Friday reported 136 new cases in the 24 hours to 8pm Thursday, Victorian Premier Daniel Andrews said “Sydney is on fire with this virus and we need a ring of steel put around Sydney”.
But Morrison said that at national cabinet Berejiklian had spelled out “in very specific detail the extensive lockdown” the state had in place.
“There’s nothing light about the lockdown in NSW – in Sydney, I can assure you. My family are in it,” he said.
At her news conference on Friday morning, Berejiklian said Chief Health Officer Kerry Chant and her team “advised us that the situation that exists now in NSW, namely around south-western and now western Sydney suburbs, is regarded as a national emergency.”
She appealed for the vaccination strategy to be redirected to south western Sydney, particularly to younger people who had to perform essential work such as the production of food.
She said there was a very young population in the affected communities, “and we need at least more first doses of Pfizer.”
Meanwhile, figures given to the Senate COVID committee showed only 47.2% of residential aged care workers had had a first vaccine dose and 27.8% had received their second dose. Vaccination has been made mandatory by September for these workers.
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 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.
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