A flu vaccination centre in suburban Preston is among Melbourne's latest coronavirus exposure sites.
Preston City Hall was declared a tier-one site on Friday, day one of Victoria's week-long lockdown.
Anyone who was at the hall between 9.30-11am on May 22 must get tested and quarantine for 14 days.
As the state entered its fourth lockdown, the number of public exposure sites grew to 127 and the military was called on to help monitor thousands of people self-isolating.
Acting Premier James Merlino on Friday confirmed four new cases were linked to the City of Whittlesea cluster, which has grown to 30 since the start of the week.
All have the B1617 strain of the virus, first identified in India, which authorities believe could be 50 per cent more transmissible than other variants.
There are now more than 15,000 primary and secondary contacts who have been told to self-isolate after coming into contact with a COVID-positive case, as well as 150 public and private exposure sites across the state.
Mr Merlino confirmed he has requested Australia Defence Force assistance to check on positive cases and their close contacts to ensure they are staying at home.
"The request will be for around 160 ADF staff for at least the next fortnight to assist our authorised offices in doorknocking positive cases, doorknocking primary close contacts," he told reporters.
"We are effectively doubling our capacity to do that really important work."
Authorities are also urgently trying to track down people who attended five exposure sites: The Sporting Globe in Mordialloc, Three Monkeys and Somewhere Bar in Prahran, The Local in Port Melbourne, and The Palace Hotel in South Melbourne.
"If you've been to those locations, you've been out partying with somebody who was COVID-positive," the state's head of testing Jeroen Weimar said.
Mr Weimar said one case contracted the virus at The Sporting Globe in Mordialloc on May 23.
It is the first case of community transmission in the outbreak.
"We're very keen to exclude, as quickly as we can, whether there's been any other community transmission at those venues," he said.
A record 47,462 Victorians were tested in the 24 hours to Friday morning, while 17,223 received a COVID-19 vaccine dose.
Mr Merlino received his first dose of the Pfizer COVID-19 vaccine on Friday afternoon, following the state's decision to open up eligibility to Victorians aged 40 to 49.
He said there was incredible demand for the vaccine within that demographic.
State Opposition Leader Michael O'Brien likewise had a vaccination on Friday.
The state's coronavirus hotline was flooded with more than 77,000 calls in 15 minutes when it was announced on Thursday that eligibility would be broadened.
Mr Weimar said 10,000 bookings were confirmed on Thursday, while more than 2000 bookings were made before 9am on Friday.
He urged people to call back later if they were struggling to get through, rather than turning up at mass vaccination centres.
More staff have been assigned to answer calls, while work is underway on an online booking system, Mr Weimar added.
As of 11:59pm on Thursday, Victorians are only allowed to leave home to shop for food and essential items, to provide or receive care, for exercise, work or study, or to get vaccinated.
People must observe a five-kilometre travel limit for exercise and shopping and wear masks both indoors and outdoors.
The lockdown is the state's fourth and it is set to end at 11.59pm on June 3.
It is expected to cost Victorian businesses up to $1 billion, with the state government set to announce a support package soon.
Federal Health Minister Greg Hunt ruled out Commonwealth support for affected businesses.
The state opposition said "businesses have been all but forgotten" during lockdown preparations.
There are 39 active cases in total in Victoria, including two new cases in hotel quarantine.