An Omicron subvariant of COVID-19 that can evade vaccine immunity is on the rise in Victoria, with authorities warning it is on track to be the state's major strain in line with virus spread in NSW and Queensland.
Traces of BA.4/BA.5 in Victoria's metro and regional wastewater have "risen significantly in recent weeks, indicating increasing transmission", says Chief Health Officer Brett Sutton.
First identified in catchments in April, the so called sublineage accounts for 17 per cent of Victorian infections and is forecast to overtake BA.2 as the state's dominant strain within weeks.
Professor Sutton says the lifting numbers follow similar patterns in NSW and Queensland.
"The department of health anticipates the prevalence of BA.4/BA.5 in Victoria is likely to result in an increase in cases, including reinfections and hospital admissions," he said on Saturday.
"This is because the strain has a greater ability than BA.2 to evade immunity provided by vaccination and earlier COVID-19 infection."
There is no evidence at this stage that BA.4/BA.5 causes more severe disease but authorities are "closely monitoring the situation".
Medical experts last week renewed calls for people to get boosters in the wake of rising infections and hospitalisations.
More than 45,000 new COVID-19 cases and 80 deaths have been recorded nationally this weekend with Sunday data still to come from South Australia and Western Australia.
There are more than 227,000 active cases nationwide and almost 3,100 patients in hospital care.
Despite the arrival of winter, vaccine and mask mandates are being eased in some parts of the country.
Several states have started unwinding restrictions including allowing unvaccinated school staff back to work, lifting bans on unvaccinated visitors at nursing homes or relaxing mask requirements at airports.
Meanwhile the number of people who have used Dine and Discover vouchers issued by the NSW government to boost financial recovery from the pandemic is surprisingly low, according to the state opposition.
Labor says department of customer service data shows that with just days to go until the vouchers expire, only 58 per cent have been spent statewide.
COVID-19 data over last 24 hours:
NSW: 7461 cases, seven deaths, 1465 in hospital with 48 in ICUs
Victoria: 5824 cases, 15 deaths, 451 in hospital, 28 in ICUs
Queensland: 3048 cases, two deaths, 556 in hospital, eight in ICUs
ACT: 819 cases, no deaths, 116 in hospital, one in ICU
Tasmania: 777 cases, no deaths, 48 in hospital, three in ICUs
Northern Territory: 221 cases, no deaths, 16 in hospital, none in ICUs