The Department of Health on Wednesday afternoon said it was investigating a confirmed case and would provide more information shortly.

Earlier in the day, authorities had warned Victorians will not get an early rules reprieve despite the state notching its first COVID-19 clean sheet since the fifth lockdown.

COVID-19 commander Jeroen Weimar said it was cause for quiet celebration and satisfaction.

"It's a symbolic marking of a point where there's no more Covid cases," he told reporters.

"It means we're on track with the strategy that we set three or four weeks ago."

But it has not inspired health officials to bring forward a review on restrictions and the current batch will remain in place until August 10.

"We still have active cases in our community right here that we know about... we've still got just under 3000 primary close contacts... and we still have ongoing risks in the rest of the eastern seaboard," he said.

He noted it was only a week ago that officials were caught off guard by the unlinked case of a Moonee Valley testing site traffic controller.

It remains unclear how the man caught the virus, but Mr Weimar said a review into the source of his infection would ramp up on Wednesday afternoon.

"There's a strong line of investigation around some movements that he had at work," he said.

Premier Daniel Andrews similarly cited Sydney's Delta outbreak as a reason for the state to take "cautious steps" towards greater freedoms.

"I fully acknowledge that there are some rules that are on at the moment that are very difficult, but they are nothing compared to being locked down again," he said outside parliament.

Earlier, 12pm: Restrictions will remain in Victoria until at least next week as the state records zero new COVID-19 cases in a 24-hour period for the first time in more than three weeks.

The latest figures released by the health department showed it was the first time Victoria did not record any new cases since July 11.

The zero day was detected from 30,117 test results processed on Tuesday.

There are now 99 active cases of coronavirus in the state, including those in hotel quarantine.

State testing commander Jeroen Weimar said restrictions would remain in place until at least next week as the state still has 93 active cases.

"At this point in time, the restrictions going on at the moment will be in place until certainly next week," he said on Wednesday.

"Obviously Brett and the rest of the team continues to review the epidemiology.

"Right now this is a good day and an important day going forward, we'll see over the coming days whether we've maintained this kind of trend."

Nine Victorians are still in hospital with COVID-19, with two in intensive care on ventilators.

Victoria is now down to fewer than 3000 close contacts who continue to isolate.

"These outbreaks are not over until we've got everyone, until all remaining leads have been closed down and all exposure sites released," Mr Weimar said.

"It's a symbolic marking of the point where there's no more COVID cases and we've dealt with yet another outbreak here in the state.

"It's the second time we've taken a Delta outbreak from zero all the way back down to zero again, I think the only place in the world that has done that and that's something that all Victorians collectively have striven so hard to get us to where we are today."

There will be more opportunities for people to get vaccinated from next month with thousands of AstraZeneca appointments opened up with walk-ins available on top of the 200,000 people who are already booked in for Pfizer.

An additional 60,000 Pfizer bookings will be made available at state run vaccination clinics in the coming months.

However, Mr Weimar said eligibility would not be furthered opened up to young people.

"We will continue to work within the national program and as that continues to evolve over the weeks ahead we'll do all we can to follow it.

"We're seeing really good penetration levels now amongst the over 40s and we're keen to ensure those more vulnerable members of the community get done."

More disadvantaged parts of Australia, including COVID-hit southwest Sydney, have some of the country's lowest vaccination rates.

Ballarat has more vaccinated people than the majority of people, but is lagging behind Bendigo and Geelong.

Almost one in four people aged of 15 are fully vaccinated in Ballarat.

Just 14.6 per cent of people aged 15 and older in southwest Sydney have received both vaccine doses as the city's coronavirus outbreak worsens.

The federal government has released data detailing vaccination rates across Australia from the start of the rollout up until Sunday.

None of the people hospitalised in Victoria with coronavirus following a recent Delta strain outbreak was fully vaccinated, although two had been given their first jab.

In his daily update on Tuesday, Chief Health Officer Brett Sutton said there were 10 COVID-19 positive patients in hospital, two of whom were in intensive care including one on a ventilator.

Statistics, obtained by AAP, show two of those cases were partially vaccinated before their admission to hospital.

Five patients were eligible but had not received their first dose, two were ineligible as they were under 40 years, and one was an unvaccinated returned traveller in hotel quarantine.

Of the two partially vaccinated people, one was in their 50s and the other 70 years and over.

Meanwhile, the Victorian-NSW border bubble tightened for residents from 11.59pm on Tuesday, banning non-essential movement across state lines.

Border bubble residents are now only able to state-hop for six reasons including medical care, compassionate purposes, work, education, playing sport or getting vaccinated.

In another change taking effect in Victoria from Wednesday, group booking limits have been scrapped for hospitality venues, tours and gyms but density limits remain.

On the back of the state's third day without a "wild" case, Professor Sutton said authorities would consider removing a ban on home visits at the end of the current two-week restrictions on August 10.

"We'll have a long tail to this outbreak," he said on Tuesday.

"There might be a week or more of a trickle of cases and we need to make sure we can clear those remaining 3000 primary close contacts, and make sure no one has been out in the community during their potentially infectious period that might kick this off again."

- With Australian Associated Press

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