Victoria is in a "precarious position" on the first full day of its sixth lockdown, as authorities race to suppress two separate outbreaks of the Delta coronavirus variant.
The state recorded six locally acquired cases of COVID-19 on Friday, two of which were announced by authorities on Thursday.
All were linked to previous cases and have been in the community while infectious.
Three of the cases are relatives of a Hobsons Bay couple aged in their 20s, one of whom works as a teacher at Al-Taqwa College in Truganina.
The remaining three cases are linked to a man in his 20s, who lives in the Maribyrnong area and works at a warehouse in Derrimut.
They are a housemate of the man, who works as a contracted cleaner at Richmond's Epworth Hospital, and two contacts from another household in Wyndham Vale, including a student at Warringa Park specialist school in Hoppers Crossing.
The Epworth said the cleaner works in consulting suites, adjacent to the hospital, and did not come into contact with patients.
It's still not known how either the Hobsons Bay couple and the Maribyrnong man contracted the virus, but initial genomic testing has confirmed they have the highly infectious Delta strain.
"Victoria is in a precarious position when it comes to where this particular series of outbreaks are," Health Minister Martin Foley told reporters on Friday.
"It is in all of our hands. We have driven down this Delta variant and we can do it again."
There are more than 10,000 close contacts of positive cases self-isolating and more than 60 exposure sites across the state, though COVID-19 Commander Jeroen Weimar has warned the list will grow.
"We'll see exposure sites start to spread across wider parts of the city and potentially regional Victoria," he said.
Virgin flights and terminal three at Tullamarine airport are among exposure sites linked to a positive case who travelled from NSW to Tasmania through Melbourne.
Mr Foley acknowledged "nobody likes lockdowns" but said they would remain a feature of the nation's public health response until 70 to 80 per cent of the population was vaccinated.
"We can't rule out their future use but at the moment we're simply focused on getting ahead of this particular outbreak and avoiding the kind of catastrophe that Sydney and NSW are enduring," he said.
Mr Foley hoped the state would be able to provide the AstraZeneca COVID-19 vaccine through its hubs for those under 60 who want it by next week, while the government has called on the Commonwealth to bring forward 150,000 allocated Pfizer doses due to "enormous unmet demand".
There are six people in hospital battling the virus, including two in intensive care on ventilators.
The seven-day, statewide lockdown took effect at 8pm on Thursday, with the same stay-home rules that applied during last month's lockdown reimposed.
Regional Victoria was included partly because of COVID-19 wastewater detections in Wangaratta, though the local mayor has said subsequent tests came back negative.
Victorians were given less than four hours notice, with authorities keen to avoid a repeat of an outbreak that occurred at a restaurant on the eve of the last lockdown.
A further $400 million will be provided for businesses affected by the latest lockdown.
Meanwhile, 15 protesters were arrested after rallying against the lockdown in Melbourne's CBD overnight.
Police said the rally was fuelled by serial protesters posing as lockdown-hit business owners and community members.
For exposure sites visit www.coronavirus.vic.gov.au/exposure-sites
Australian Associated Press
