Months of rolling lockdown in Victoria

Epidemiologists advising the state and federal governments say Victorians will endure more frequent lockdowns until the end of the year because of Sydney’s worsening outbreak and the high infectiousness of the Delta variant of COVID-19.

The most recent modelling of possible outbreak scenarios predicts Victoria could spend at least one in four days under lockdown, while other scenarios predict even more frequent lockdowns will be required to contain the spread of the virus.

The chain reaction

NSW reported a record-high 291 new cases last Friday in a worsening outbreak that experts from Melbourne and Monash universities say will contribute to more frequent outbreaks – and lockdowns – in Victoria.

Victoria was out of lockdown for just over a week before stay-at-home orders were imposed for another seven days from 8pm Thursday, after the detection of six new cases in the community. The state on Friday recorded six new cases of coronavirus linked to existing outbreaks, but the infected people were not in quarantine while infectious.

Monash University’s epidemiology team, which provides Victorian and federal government modelling, now assumes Sydney will not bring its caseload to zero over the next few months.

The way to cope with it

Team head James Trauer said Victoria could expect to cycle through lockdowns until vaccine coverage of 70 or 80 per cent was reached.

Another member of the Monash team, Michael Lydeamore, said: “Delta is so much more transmissible that the likelihood of control using only our existing measures, but without lockdown, is very small.”

/ Member of the Monash team, Michael Lydeamore

150,000 extra doses of the Pfizer vaccine would be brought forward for Victoria in response to a request from Premier Daniel Andrews. It follows the federal government last Thursday bringing forward the delivery of nearly 185,000 jabs for NSW and 112,300 for Qld, which has also locked down to suppress the virus.

Modelling by the Doherty Institute commissioned by the federal government suggests lockdowns are needed about 40 per cent of the time while less than half the Australian population is vaccinated. This model assumes light restrictions are in place at all times and there are low levels of circulating virus when emerging from lockdown. Importantly, it does not account for periods when the virus is eliminated and could therefore overestimate the amount of time spent in lockdown.

Delta is now the game changer

University of Melbourne modelling published in JAMA Health Forum last week suggested Melbourne could expect to spend about a quarter of the year in lockdown. That modelling could underestimate the extent of disruption as it was conducted with data from the coronavirus strain that first emerged from the Chinese city of Wuhan, not the Delta variant circulating in Australia.

Delta is about 60 per cent more infectious than the Alpha variant of the virus, which in turn was perhaps 50 per cent more contagious than the strain of the virus that emerged in Wuhan.

The University of Melbourne modelling assumed there was a one in 100 chance per day of a new case being seeded in Victoria, but with Sydney’s worsening case numbers that threat has increased.

“If your strategy is ‘go hard, go early’, but you can’t control the incursions, you’re going to be doing it a lot. So you have to control quarantine, and the border, and the incursions. That’s it, really because otherwise you are in permanent lockdown,” Dr Thompson said.