Authorities have urged around 2 million eligible Victorians to book in for their booster shot immediately, after the state reported another 31 COVID-19 deaths.
Speaking at the daily press conference, Victorian COVID-19 response commander Jeroen Weimar said two vaccine doses did not offer full protection against Omicron.
"Unfortunately, the COVID pandemic continues to evolve, and we need to evolve with it," he said.
"We'll wait to see what National Cabinet decides in the coming weeks around the definition of what fully vaccinated means, but if you get a booster, you're far less likely to end up in hospital because of Omicron."
Victorian Premier Daniel Andrews has been pushing for the definition of "fully vaccinated" to be updated to refer to three vaccine doses, but the Prime Minister's office says they do not want to pre-empt ATAGI, the key advisory group on immunisation.
Mr Weimar said about 4 million Victorians in total were eligible for the third dose vaccination, but just under 2 million — or 37 per cent of Victorians aged over 18 — had received the booster.
He said more than half of those aged over 60 and 62 per cent of those aged over 70 had received their booster.
There are 953 COVID-19 patients in Victorian hospitals, down from 988 on Friday.
Of those in hospital, 114 patients are in intensive care and 39 are on ventilators.
The state has reported 12,250 new COVID-19 infections that came from 6,244 PCR tests and 6,006 rapid antigen tests.
It takes the official number of active cases in the state to 79,836, well down from figures of more than 200,000 in mid-January.
While the government and epidemiologists believe Victoria is past the main peak of Omicron infections, cases are expected to rise when students return to classroom learning on Monday.
School pop-up vaccination sites open over weekend
Health officials are urging parents to get children aged five to 11 years vaccinated before school begins and the government has opened more pop-up vaccination clinics across Victoria.
Mr Weimar said there were more than 6,500 vaccination appointments available across the weekend for children in the younger age bracket.
He said parents had a number of options from GPs to chemists, as well as walk-in hubs, including at Dandenong Plaza, Royal Exhibition Building and Sunshine Hospital.
He said there were 15 school pop-up vaccination sites running over the weekend, with the details listed on the health department's website.
"As we see people coming together again through to the school environment there will be more opportunities for transmission," Mr Weimar said.
"The issue for us is putting those additional measures in place where we manage that as effectively as we can to minimise onward impact."
According to the Health Department, 231,286 children aged five to 11 years have now received a paediatric dose of COVID-19 vaccine in Victoria, which is 40 per cent of that age group.
Idris Khalid, who had taken his children Imran and Atiya to get vaccinated at a pop-up centre, said he and his wife discussed what to do, keeping in mind the "chaos" of Omicron.
"Kids need vaccination because it gives protection and immunity against the virus," Mr Khalid said.
"We don't want kids to go to hospital.
Cases of Omicron subvariant detected in Victoria
Mr Weimar said Victoria had recorded a "handful" of the Omicron subvariant, the BA.2.
The subvariant is nicknamed the "stealth" variant and has been reported in more than 40 countries.
Mr Weimar said Victorian authorities were monitoring the situation closely.
"I am aware there's a very small number of cases that have been detected here in Victoria," he said.
"It's still very early days just understanding exactly how that's moving around.
