Melbourne's stage 3 lockdown prevented thousands of coronavirus cases, research data shows

Lockdown restrictions in Melbourne during July prevented almost 19,000 people from contracting COVID-19, according to new data.

Researchers from the Burnet Institute predicted about 27,000 people would have been diagnosed with coronavirus in July had the growth rate in Victoria continued unchecked.

Instead, just over 8,000 people with locally-acquired infections were diagnosed in Victoria.

The researchers modelled scenarios and found in the worst case, there could have potentially been up to 45,000 cases — meaning up to 37,000 cases could have been avoided.

Burnet Institute CEO Brendan Crabb said overwhelmingly, community effort in adhering to stage 3 restrictions had a "major impact" in preventing cases and saving lives.

"We can assume we would have had three to four times the number of deaths, three to four times the number of serious illnesses, so a very major impact of stage 3 lockdown," Professor Crabb said.

Stage three restrictions in Melbourne and Mitchell Shire included closing pubs, bars, entertainment venues, places of worship, restricting restaurants and cafes to take-away only and limiting public gatherings to two people

There was also a complete quarantine and isolation imposed in several high-rise public housing estates.

The study found the reproduction rate of the virus before the lockdowns was 1.75 — meaning for every 10 people infected with the virus, more than 17 others caught it.

In the month of July, that reproduction rate was reduced to 1.16 — meaning just over 11 people were catching it from every 10 infected.

UNSW epidemiologist Marylouise McLaws said the restrictions were necessary once COVID-19 patient numbers started increasing.

"After June, the numbers in Melbourne were stubbornly high and once you get to more than 100 cases a day, then it can accelerate the next 14 days and increase five-fold," Professor McLaws said.

She said more than 40 per cent of people in Melbourne had jobs you couldn't do at home and were employed as part-time or casuals working multiple jobs.

"They probably went to work and had over 10 contacts every day, and the risk of them picking it up and transmitting the virus was high," she said.

Stage 4 restrictions needed

While the study's findings showed that stage 3 restrictions worked well, experts said Victoria still faced a "huge challenge to reduce transmissions to the level needed to get the COVID-19 epidemic under control".

The findings come as residents of Melbourne and Victoria face stricter lockdown measures to stem the rising tide of cases.

In Melbourne, where stage 4 restrictions have come into place, movement of people is curtailed and thousands of businesses have been shut down for the next six weeks.

Professor Crabb said the epidemic was still not in decline and community spread of the virus was still growing.

"We have the rate decreasing but not yet an epidemic going down to zero — to elimination — which is where we want to get to in the community," he said.

Melbourne tiring of restrictions

The challenge is now "community fatigue"' setting in, which might see more people not wanting to adhere to stage 4 restrictions.

To counter that, getting different communities on board with public health messaging is crucial.

"Most of the initial measures to control COVID-19 … have been top-down control, community cooperation is essential," the Burnet Institute study said.

The authors said local community leaders should be engaged, to encourage them to lead their own communities in the response to the virus.

Professor McLaws said the approach to public health messaging had been "very white, middle-class".

"The messages assume you speak English and access mainstream media and that's not necessarily the case for young people and multicultural groups," she said.

"They may not be hearing it."

Advertising specialist Dee Madigan agreed.

"What we are seeing is that Government messages are working on a particular cohort and not working on other people," she said.

"They are working particularly well on educated women, over the age of 35.

"Once you look at people with lower education and also in lower age, they're less likely to follow the Government's recommendations."

She said these people were also more likely to be in insecure work and not have savings.

"I think to change any behaviour, you need a carrot and a stick.

"I am not sure what the carrot would be but it doesn't feel like there is much beyond the fact that hopefully at the end of the next six weeks we might get to stop this."