Scott Morrison insisted Victoria has enough coronavirus vaccines after the sluggish federal rollout was blamed for its lockdown-inducing outbreak.
The state government is hopeful its seven-day shutdown will be a circuit-breaker after 11 new infections took Melbourne's virus cluster to 26.
There is one COVID-19 case in hospital in Victoria. This case was in intensive care but has now moved back to the ward.
Acting Premier James Merlino said the lockdown might not have been necessary had the Commonwealth effectively rolled out vaccines.
But the prime minister quoted Mr Merlino saying there were ample vaccine supplies, with an extra 130,000 being sent to Victoria in response to the outbreak.
"Whether it is Victoria, Western Australia, up in far north Queensland, our simple message to you is: the vaccines are there," Mr Morrison told reporters in Canberra on Thursday.
"Make a booking, talk to your doctor, please get vaccinated."
Chief Health Officer Brett Sutton said the state could ramp up towards administering 100,000 doses a week if extra supplies were provided.
Along with social and business restrictions, Victoria is also extending eligibility for the Pfizer vaccine to people aged between 40 and 49.
Federal Health Minister Greg Hunt said 660,000 doses of the two dual-dose vaccines had been delivered to Victoria since the start of the rollout with 398,000 administered.
He said Australia was receiving about 350,000 doses of Pfizer and one million of AstraZeneca a week, with about 2.7 million held for second jabs and other contingencies.
It comes as another six AstraZeneca vaccine-linked blood clot cases were confirmed by Australia's medicines regulator on Thursday, taking the total number to 27.
A further three cases were also listed as probable.
Of the millions of AstraZeneca doses already administered across the country there has been one fatal case so far, a 48-year-old NSW woman.
Meanwhile, Opposition Leader Anthony Albanese criticised the government for failing to establish more dedicated quarantine centres and slow vaccine progress.
"The government had two jobs this year: to get quarantine right and to get the rollout of the vaccine right," he told reporters in Canberra.
The prime minister gave his strongest show of support for a state government plan to establish a 500-bed quarantine facility on Melbourne's northern fringe.
Mr Morrison believes the construction start date of September can be brought forward, allowing the hub to be up and running sooner than predicted.
The flare-up was sparked by a man who caught coronavirus while in hotel quarantine in Adelaide before travelling to Melbourne.
This is the 17th outbreak from hotel quarantine in the past six months.
Experts have repeatedly urged the prime minister to put in place dedicated facilities to take pressure off hotels that were built for tourism, not medical quarantine.
Mr Merlino emphasised the hotel quarantine breach when announcing the fourth statewide lockdown.
"If we had an alternative to hotel quarantine for this particular variant of concern, we would not be here today," he said.
"If we had the Commonwealth's vaccine program effectively rolled out, we may well not be here today."
The federal opposition labelled as a scandal reports that almost 30 aged care facilities have not received any vaccines.
Mr Hunt said the number had fallen to 16, with seven to be completed on Thursday and the remaining nine on Friday.
To assist, a shorter interval between flu and COVID-19 shots given to staff and residents of aged care facilities has been approved.
Australia has designated Melbourne as a virus hotspot, with all states and territories imposing travel restrictions or outright border closures in response to the Victorian outbreak.