Victoria "right on the edge" as majority of 57 new COVID cases were infectious in community

"If we have a weekend this weekend like last weekend, well then next week it will be like Sydney. Simple as that. This will get away from us,"  Victorian Premier Daniel Andrews said.

Victoria may be facing its toughest challenge yet in 2021 as the state reports 55 new locally acquired COVID-19 cases of whom only 25 were in isolation for the entirety of their infectious period.

"That is a very significant challenge. That makes today a bad day," Premier Daniel Andrews said.

In the 24 hours to midnight last night there were also two new cases in hotel quarantine, and of all new cases 49 are linked to known outbreaks and six are currently mystery cases under investigation.

The Premier said the government could not have locked down any earlier than it did and is playing its part, but the rules are "only as good as the behaviour and the choices that each of us make".

"We've got too many mystery cases out there. We need people to come forward and get tested when they have symptom; not a day later, not three days later," he said.

"It's not about looking for every loophole, every exemption, every sort of blind corner where people can't see you, to do the wrong thing."

He said the Delta variant was so wildly infectious that it would find every breach of every rule and will potentially spread because of that.

"It's not just delicate, it's not just a tipping point. We are right on the edge of this getting away from us," he said.

"We all have to make choices that recognise how serious this is. There are 700 kids that have got COVID in NSW. There are kids that are in hospital in NSW that have got COVID - no children in our country are vaccinated.

"As a parent to every other parent, that should be motivation enough. We can't be certain what the impacts of this virus are on kids. We have got a substantial number of kids infected ourselves in this outbreak - it is spreading amongst younger people and it will continue to do that unless we all play our part."

There are currently 349 active cases of COVID-19 in the state.

In more positive news, there were almost 50,000 tests in Victoria yesterday and 28,601 vaccinations administered by state clinics.

"I thank all of those nearly 30,000 people who made an appointment, kept their appointment, turned up and got the jab. That's such an important thing or you to do," he said.

"There are appointments open as we speak. Thousands of them...if you go to the website you can book, and you can book with confidence."

Updated at 12:40pm AEST on 20 August 2021.