Victoria has recorded 80 new coronavirus cases since Wednesday - the highest daily case number since September 2 in 2020.

The new COVID-19 cases are all locally acquired with 67 linked to current outbreaks and 39 in isolation during their infectious period.

Victoria's active coronavirus case tally now stands at 600, with 240 infections in young Victorians under the age of 20. There are still 40 mystery cases in Victoria where the source of infection is unknown.

There are 36 Victorians in hospital, with 23 of those under the age of 50, one an infant, 11 in intensive care and eight on a ventilator.

Meanwhile New South Wales recorded 1029 new COVID-19 cases and three more deaths today.

Almost 80 per cent of intensive care beds in that state remain full.

Wednesday also bought 56,248 test results to Victorians as well as 33,932 vaccinations being administered - the biggest day of vaccines the state has ever seen.

Victorian Premier Daniel Andrews said many of today's new cases were infected people who waited "too long" to get tested.

"If everyone gets tested as soon as they register symptoms we will slow down the spread and we will drive down the number of cases and protect more people from serious illness, hospitalisation and even worse than that."

More than 95,000 Victorians booked vaccine appointments at state-run hubs to 4pm on Wednesday, despite the online system being overwhelmed as Pfizer eligibility expanded to those aged 16 to 39.

Premier Andrews encouraged people to be patient and persevere with the state vaccination website.

"I'd encourage people to go back online; you have to be patient, there's no choice," he said.

"But there are more appointments being made, in fact 200,000 of them were made yesterday."

The outbreak has hit Victoria's health system and is causing distress in the regional town of Shepparton, with 18 more cases today bringing the cluster to 67 cases.

The state's exposure sites list has ballooned past 800, including the emergency department of Monash Medical Centre which is now listed as a tier one exposure site.

Victoria is recruiting 350 overseas doctors and nurses to ease pressure on a hospital system facing hundreds of workers being furloughed due to coronavirus exposure, including at Royal Melbourne Hospital and Goulburn Valley Health.

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The Goulburn Valley is battling an outbreak centred in Shepparton with at least 50 cases and 17,000 residents in isolation.

Among those told to quarantine are supermarket staff, prompting many shops to close for cleaning, limiting access to essential supplies.

Yesterday 25,000 first-dose vaccines were administered across Victoria.

Victorian coronavirus testing commander Jeroen Weimar said AstraZeneca bookings under 40s that were made before the eligibility was changed will be converted to Pfizer bookings.

Any AstraZeneca bookings made from today onwards, you will be offered AstraZeneca.

"Let me be very clear, whatever age you are, if you book an AstraZeneca appointment today or tomorrow, you will be offered AstraZeneca alone when you turn off your vaccination," Mr Weimar said.

Victorian's Chief Health Officer Brett Sutton said household transmission continues to be one of the biggest spreaders of this Delta outbreak.

"In particular we've seen transmission from children to adults within households," he said.

"This virus has moved silently and with stealth across Melbourne and into regional Victoria... You are at risk if you are in Victoria or Australia.

"What has become apparent in recent weeks is that maybe three-quarters of transmission with the Delta variant occurs without symptoms or before you've developed symptoms."

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