New modelling released today shows Sydney’s current level of social distancing is still not enough to control the outbreak.
The University of Sydney modelling studied the movements of people during the period between July 16-25, and found that while social distancing had improved compared to the two weeks before that, it is still too low to control the Delta outbreak.
Professor Mikhail Prokopenko, director of the University of Sydney’s Centre for Complex Systems, told news.com.au the model showed social distancing had improved from 40 per cent to around 60 per cent.
But this was still short of the 70-80 per cent needed in order to drive down cases to below 10 a day within a month.
“What is most concerning is that our model showed that even when we take into account essential workers, 10-15 per cent of the population is still not doing the right thing which means we could be stuck in lockdown for quite a while longer,” Prof Prokopenko said.
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Prof Prokopenko said the modelling also showed the growth rate of Covid-19 cases in NSW had slowed, although this did not take into account today’s record 239 cases.
The modelling looked at cases up until Sunday, July 25 and found in the two weeks prior, the seven-day moving average dropped to 3.7 per cent, from a growth rate of 10 per cent in the two weeks prior to that.
“The rate is slowing so that’s positive but it’s not slowing fast enough,” Prof Prokopenko said.
“One reason is that the strict lockdown was not imposed early enough.”
He said the modelling, which has been released as a pre-print today, showed the impact of NSW’s decision to wait two weeks before locking down more strictly.
It also revealed the impact of increasing rates of vaccination will not come into play for at least a month.
Prof Prokopenko said if a strict lockdown — similar to Stage 4 restrictions but not including a curfew or a 5km limit — had been introduced when there were only 100 cases in Sydney (around June 24), this would have seen cases go up for two weeks but then come down, with the outbreak under control a month later. This could have seen Greater Sydney coming out of lockdown by mid-August — just two weeks from now.
But the model showed that waiting two weeks until cases had reached a cumulative total of 400 (around July 9) to introduce the harsh lockdown, meant cases would not come down until around mid September at the earliest, even though around 40 per cent of people were expected to be vaccinated by this time.
“What this tells us is that this delay in locking down, essentially cancels out (the benefit) of progressive vaccination,” Prof Prokopenko said.
“At this stage lockdown makes a larger impact than progressive vaccination.”
However, Prof Prokopenko said the “balance will tip” and vaccination would come into play after a couple more months.