Record levels of COVID-19 cases have forced a change in the way Victoria processes PCR tests, leaving many waiting longer than usual for results.
Victoria recorded another all-time high of 8577 new COVID-19 cases and a further three virus-related deaths on Monday.
With the daily record again tumbling, the state's COVID-19 commander Jeroen Weimar has apologised for delays in some people receiving test results.
One man told AAP he has been waiting almost five days for his result and was yet to receive it as of 1pm on Monday, after taking a PCR test at Melbourne Town Hall on December 29.
Mr Weimar says nine out of 10 PCR test results were previously being returned within a day, but that figure has dropped to a third and another half are coming back the next day.
Because of the level of virus in circulation, he explained, PCR swabs can no longer be collectively tested and then re-tested if a positive result is identified among them.
They must instead be tested one by one, leading to longer turnaround times.
"We're now seeing one in five cases who are being tested in a PCR system is now positive. That's a tenfold increase in the space of the last couple of weeks," Mr Weimar said.
"Normally ... it's around a two per cent positivity rate."
Virus testers processed 44,168 results in the 24 hours to Sunday evening, reflecting another fall in PCR swab rates likely linked to an increased emphasis on rapid antigen testing.
Victorians have been struggling to get their hands on RAT kits, with shelves stripped bare at chemists and pharmacies in Melbourne.
Chemist Warehouse chief operating officer Mario Tascone says the retailer is flying in half a million RAT kits every second day, but it still isn't enough to meet current demand.
"You've got to understand - 24 million people want a rapid antigen test. You can't fill that pipe in a week," he told Melbourne radio 3AW on Monday.
Mr Tascone said Chemist Warehouse stock levels in Victoria were effectively "down to zilch", despite most Melbourne stores receiving "healthy" deliveries on Saturday afternoon and Sunday.
Most stores are expected to get fresh deliveries of 500 to 600 kits on Monday afternoon or Tuesday morning.
Mr Tascone said other retailers were feeling the pinch and it would take a few weeks for the system to catch up.
"It's a perfect storm at the moment," he said.
The Victorian government has already flagged it will distribute 34 million free rapid antigen tests by the end of January.
An initial batch - containing several hundreds of thousands of rapid tests - is expected to arrive this week, Health Minister Martin Foley says.
Anyone who returns a positive rapid test is encouraged to get a PCR swab and isolate until they receive their result.
Community sampling has shown 76 per cent of all COVID-19 samples collected over the Christmas period are the Omicron variant.
More than 23,000 cases have been reported in the first three days of 2022, greater than the entire number throughout 2020.
"It shows you how fast Omicron is moving across the eastern seaboard," Mr Weimar said.
Some 10.9 per cent of Victorians 12 and above have had their booster shots, ahead of the interval from second to third doses shortening to four months from Tuesday.
VICTORIA'S LATEST COVID-19 FIGURES:
* Active cases: 38,118
* Hospital cases: 491, up 19
* Hospital cases seven-day average: 444
* Active cases in ICU: 56
* Cleared cases in ICU: 48
* Cases on a ventilator: 24