Researcher predicts NSW’s coronavirus cases will peak at more than 3100 a day

A researcher studying NSW’s highly infectious Delta outbreak has predicted when the vaccination rate will finally start to bring cases down.

It’s the big question that has haunted Sydneysiders in lockdown for months: when will NSW finally flatten the curve of rising Covid-19 infections?

Experts believe they can now answer that question. But the bad news is that the situation will get worse before it gets better.

According to modelling prepared by Melbourne University’s Chris Billington, the outbreak is on track to hit a peak around September 22.

“We can expect the cases to peak at between 2200 and 4500 cases per day,” he told news.com.au.

“And the median there is about 3100.”

NSW R_eff as of August 30th with daily cases and restrictions. Latest estimate: R_eff = 1.36 ± 0.06

Plus projected effect of vaccination rollout.

Cases shown on a linear scale (log scale in next tweet).

More info https://t.co/OWkU79AITX#covid19nsw#covidsydneypic.twitter.com/oORex1lexv

— Chris Billington (@Chrisbilbo) August 30, 2021

NSW Premier Gladys Berejiklian did not deny that the coming weeks are going to be the toughest.

“We are hopeful that once we get those vaccination rates up, the rate of hospitalisation declines,’’ she said.

“We also know from the information we have, the accumulation of cases and the number unvaccinated, that October is likely to be our worst month in terms of pressure on the system and that’s why we have been gearing up for that and we have been for nearly two years.”

In Victoria, the modelling suggests that numbers will peak at around 200 cases a day around the same time.

“Anywhere between 100 and 500 cases per day,” he said.

“So that’s a very big uncertainty range. The middle of that, which is the most likely peak, is about 200 cases per day.”

But that’s as bad as it will get if restrictions are not eased, before the numbers fall in October.

What’s significant about the Melbourne University researchers’ work is that it factors into the equation the impact of vaccines in slowing the pace of the infections into the estimate on when numbers will peak and fall.

Current projection after incorporating today's NSW case number is at 3100 cases per day (range: 2200 to 4500), in late September. Picture: Chris Billington/Melbourne University

That moment is when the number of Australians who are vaccinated will start to bring down the reproduction rate or ‘R’ rating which tracks the number of people that each person with the virus will infect before they recover.

If the reproduction number of a disease can be brought below one, then the spread will slow until the virus numbers decline.

The consistent doubling of cases in a fixed period is the hallmark of exponential growth. At the moment, cases in NSW are doubling every 11 days.

Expected numbers if the current trend continues:

day cases 68% range
Tue: 1336 1168—1504
Wed: 1420 1217—1632
Thu: 1504 1260—1760
Fri: 1591 1309—1898
Sat: 1681 1354—2046
Sun: 1771 1391—2191
Mon: 1861 1427—2344

Doubling time is 11.2 days.

— Chris Billington (@Chrisbilbo) August 30, 2021

While the lockdowns and restrictions have slowed the spread of the virus and stopped case numbers from being even higher, it’s vaccines that now hold the key to flattening the curve of infections.

In that sense, the lockdown has also been about buying time until as many Sydneysiders as possible are vaccinated against the virus.

But to put into perspective critics who claim that “lockdowns don‘t work”, Sydney University researchers have estimated that without any restrictions the NSW outbreak could be running at 40,000 cases a day even if 80 per cent of the community was vaccinated.

“Although it is encouraging that more people are being vaccinated, we can expect to see a rapid increase in cases when we exit the lockdown,‘’ researcher Mikhail Prokopenko said.

The Sydney University research also has a darker prediction than Chris Billington’s estimate of a peak of 3100 cases in late September.

It claims that daily Covid-19 case numbers will continue to climb and could peak between 1500 and 6000 a day by early October.

“National modelling led by Centre for Complex Systems researchers shows that a pandemic peak is in sight, but we must brace for a surge of infections upon reopening when 80 per cent of the adult population is vaccinated and restrictions are lifted,” the research states.

Workers at a Covid-19 drive through test centre in Sydney. Picture: NCA NewsWire

But the good news according to Melbourne University epidemiologist and public health specialist Professor Tony Blakely is that the infection rate is already slowing.

The real benefits will kick-in in coming weeks as the exponential curve of cases is finally flattened.

“I am hopeful that it is about to turn. Certainly, I think that that is probably what‘s going to happen,” he said.

“As the vaccination coverage increases, it gets easier to control this virus. We all know that.

“However, our vaccines are not perfect. They’re far from perfect. They’re still good.

“So we’re never going to get complete control of this virus with just the vaccine so we’re going to need to keep some form of social distancing, mask wearing and all those sorts of things in place. So, we just need to keep going.”

Professor Blakely said it was still possible to get back to Covid-zero in Victoria but it wasn‘t going to be easy.

“The answer is yes. But it’s becoming pretty tough,’’ he said.

“It might take about six weeks of hard lockdown to get us back to less than five a day, which is a long haul. It‘s possible. And I notice that Premier Andrews said that he’s still going for elimination or at least getting the numbers low, which is a fair enough stance.”