Melbourne's 'magic number': When is it safe for the city to leave lockdown?

A Melbourne epidemiologist has attempted to predict the magic number Victoria needs to hit before it lifts its lockdown as the state reports its lowest number of daily new coronavirus cases in 24 days.

On Thursday, Victoria confirmed 278 new cases and eight deaths for the previous 24-hour period. The sobering number follows a day where 410 new cases were reported and a record 21 deaths.

But as Victorians receive a glimmer of hope the Stage 4 lockdown and mask mandate is prevailing, the state still has a while to go before lifting lockdown should be considered.

University of Melbourne Professor John Mathews told Yahoo News Australia Victoria would have to get its daily cases as low as NSW.

“The simplest thing is to look at NSW. They’re still under about 20 cases per day, and unless we get to at least that stage in Victoria, it would be hard to recommend stopping the lockdown,” he said.

“Because the numbers are smaller, the contact tracing is more manageable and they can track the new cases and the context down pretty quickly.”

Warning over lifting lockdown prematurely

Prof Mathews said Victoria would still be locked down for at least another five weeks, but was optimistic the virus would be suppressed to numbers similar to NSW in that time.

“But we can’t predict that with any confidence, the government has obviously made some mistakes and it’s a very difficult situation but they’ve done the best they can,” he said.

“What happened last time was with the first wave we thought we got it under control – and we did have it under control – but everybody relaxed, the government relaxed a bit – particularly with hotel quarantine – and it spread into the meatworks and the high rises, into aged-care homes and all those things kind of crept up.

“If the lockdown is relaxed prematurely then we could have exactly the same thing happen again and even in Victoria, the proportion of people infected is still very low. The only thing that can bring the outbreak under control is suppressing transmission with the lockdown and social distancing procedures.”

Why herd immunity won’t work for Victoria

Prof Mathews added the state did not have enough people who had become immune to bring the outbreak to an end.

“In overseas countries with much higher infection rates and many more people who have died, there’s some suggestion there the second wave either won’t happen or will be much smaller because enough people are either resistant or immunised from being exposed,” he said.

“It helps to bring the wave under control. In the UK, there is quite a bit of speculation the end of their outbreak may be in sight and they’re explaining that in terms of not only a high infection and death rate, but a high proportion of people being infected without having symptoms who have become protected by acquiring herd immunity.

“It remains to be proven in the UK and other overseas countries... but that’s a totally different situation to Australia. Here the infection rates are far too low to have brought about protection as a result of herd immunity. We hope it stays that way because if infection rates go up there’ll be many, many more deaths, as we’ve seen in Europe and the United States.”

Prediction for the next two weeks

Prof Mathews does not believe case numbers in Victoria will hit peaks of 700 again, but expects daily cases to hover around 300 to 400 for a few more days before it starts trending downwards over the next two weeks.

“The hope is when the extra five weeks are up, that we’re down near single-digit cases per day. That’s a hopeful prediction,” he said.

“The Stage 4 lockdown is really focused on stopping people meeting each other as much as they possibly can and getting people off the streets with the curfew and making sure people aren’t going to work for non-essential jobs.”

Prof Mathews said everybody had underestimated the difficulty of dealing with the virus and despite everybody wanting to do the right thing, there had been mistakes.

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“I think people understand the principles now,” he said.

“Things that have happened haven’t been sensible but fortunately people are learning from the mistakes that have been made.”

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