Acting Chief Health Officer Ben Cowie says the change will be reflected on the state's vaccination booking website from Thursday.

"This change and the additional supply of Pfizer vaccine from the Commonwealth, when it arrives in Victoria, will help us to reach our vaccination targets faster," he told reporters.

"But more importantly, they will really contribute to the response to community transmission, put a downward pressure on cases, and contribute to protecting the health system."

The change makes the wait time between AstraZeneca doses the same as for Pfizer, of which the state has limited supplies.

Professor Cowie said there were more than 52,000 available AstraZeneca appointments in the coming weeks.

Of the state's 176 new cases, 83 are linked to known outbreaks, with the source of the remaining 93 infections under investigation.

Health Minister Martin Foley said 67 cases were located in the northern suburbs of Melbourne, 61 in the west, 22 in the east and south, 13 in the regional town of Shepparton and one case in Geelong.

It is not yet clear how many cases have been in isolation throughout their infectious period.

He said an outbreak at a Melbourne call centre for the state's coronavirus hotline is of particular concern to authorities.

Some 17 people who work at the call centre have tested positive and 400 primary close contacts are now self-isolating.

A case at Base Backpackers in St Kilda is also a concern. The person has been moved into hotel quarantine.

There are 1029 active cases in the state, including 61 battling COVID-19 in hospital.

Twenty are in intensive care, including 13 who are on a ventilator to breathe.

It is the state's second consecutive day of more than locally acquired 100 cases, after 120 were reported on Wednesday.

The government has conceded efforts to bring cases down to zero have failed, with tough restrictions to remain in place until October.

Authorities have shifted their focus to suppressing the outbreak, keeping the health system from being overwhelmed, while racing to reach higher vaccination coverage.

Residents in COVID-hit Shepparton are flooding local testing sites, as the end of their two-week isolation approaches.

At least 112 cases have been linked to the Shepparton outbreak, which kicked off almost a fortnight ago and landed an estimated 20,000 people in isolation.

About 4000 people are due to be swabbed on Thursday, in what is the peak of day 13 testing for the region.

Most are students and teachers from schools caught up in the outbreak, including St Mel's Primary School, Bouchier Street Primary School, Notre Dame College and Greater Shepparton Secondary College.

Schools and year levels were allocated specific times to attend testing sites to prevent long queues, but all quickly reached capacity.

"Please delay coming to the testing sites if you are not already there. We will update regularly as capacity improves," Goulburn Valley Health chief executive Matt Sharp posted on social media just before 9am.

Teacher Amber Bock, 27, and firefighter Daniel Dimattina, 29, joined one of the queues at 6am on Thursday to beat the rush.

Testing opened about 8.30am and it took just over an hour to get their swabs.

"The nursing staff were fantastic," Mr Dimattina said.

Ms Bock and Mr Dimattina have been stuck in isolation since August 20 after Ms Bock's housemate - a teacher at Greater Shepparton Secondary College - was identified as a primary close contact.

Mr Dimattina, who lives in Reservoir, was visiting his Shepparton-based fiancee Ms Bock and was in the car ready to return to Melbourne when informed they needed to isolate.

While only primary close contacts require day 13 testing, both fronted up so they can return to work.

Ms Bock is one of about 10 teachers at Numurkah Secondary College who have also had to isolate, despite no cases being linked to the school yet.

She said widespread staff shortages across supermarkets, cafes and businesses have put Shepparton under "intense strain", and many of her school's students are struggling with the move to remote learning.

"We've got about 260 students but probably about 50 per cent engagement online," Ms Bock said.

"We've had to give internet dongles to families, or maybe there's five kids in the family and only one laptop."

Day 13 testing is expected to free thousands more people in the Goulburn Valley region from isolation, further easing staffing pressures.

But all must return a negative test result and wait to be formally notified by the health department before they can leave isolation.

In Melbourne, another hospital has had to furlough more staff after a worker tested positive to COVID-19.

Staff from The Alfred have been sent home to isolate as a precaution after a colleague tested positive for the virus on Wednesday.

A general medicine ward staff member contracted coronavirus as the primary close contact of another case, an Alfred Health spokeswoman said.

Close contacts at the hospital have been identified by contact tracers and are isolating, with secondary contacts being notified.

"Our priority at this time is the safety of our patients and staff," she said.

Royal Melbourne Hospital also furloughed staff after several patients, staff and visitors tested positive.

with AAP