Victoria has reported 1290 new COVID-19 infections and a further two deaths, as new research found three people in Melbourne contracted the virus for a second time.
The state is now managing 11,649 active cases despite 92 per cent of residents aged 12 having got two doses of a COVID-19 vaccine.
There are 323 patients in hospital, 77 of whom are actively infected with the virus in intensive care and 40 needing ventilation.
The seven-day hospitalisation average sits at 312.
Testers processed 55,122 results on Sunday, while 3266 people were vaccinated in state-run hubs.
The latest figures come as medical researchers discovered three people from a Melbourne household had contracted COVID-19 for a second time, one year after first becoming infected.
They tested positive for the virus in July 2020, with two of three suffering mild symptoms and the third reporting no symptoms, according to a study published in the Medical Journal of Australia on Monday.
The variant they contracted, pangolin lineage D.2, was not of concern.
Then all three contracted the Deltra strain of COVID-19 in July this year, but only experienced mild symptoms.
While second infections are believed to impact less than one per cent of people, the researchers are urging people who have contracted the virus to still get vaccinated.
"Just because you've had COVID-19 and recovered from it doesn't make you immune. You're still at risk of getting COVID-19. Our only protection at the moment is the vaccination," Monash University epidemiologist Mohana Baptista said.
Meanwhile, Victoria has lowered quarantine requirements for travellers from several countries of concern.
Fully vaccinated travellers from South Africa, Botswana, Eswatini, Lesotho, Malawi, Mozambique, Namibia and Zimbabwe are no longer required to undertake 14 days in hotel quarantine upon arrival.
They must instead self-quarantine for 72 hours, get tested within 24 hours of arrival and again between days five and seven, like other international travellers.
The state is awaiting the test results of several passengers from an international flight that carried at least two confirmed Omicron cases.
There are three Omicron cases in Victoria - a returned traveller from the Netherlands who is in hotel quarantine and two people who sat together in the same row on a flight from Dubai to Melbourne on November 30.
A third person who also sat in the row has tested positive for COVID-19 and genomic sequencing is underway to confirm the variant.
Four other passengers on the same flight and three household contacts of a case are also being tested.
Australian Associated Press
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