Health Minister Mark Butler says COVID-19 cases are not likely to peak nationally for at least four weeks during this third wave of infections.
"All of the modelling indicates that case numbers and hospitalisations have further to go over probably the next four to six weeks," he told Melbourne radio 3AW on Tuesday.
"We've seen some data out this morning that suggests that COVID is the largest killer of Australians this year, taking over from coronary disease."
Meanwhile, COVID-19 reinfections are becoming more common across the country as new sub-variants of the virus circulate.
University of Queensland Associate Professor Paul Griffin said people should not become complacent about the virus, warning those who had been recently infected could be reinfected in a matter of weeks.
"We are seeing reinfections being more common and in short intervals, and that is why we recommend the reinfection period be reduced to four weeks," he told the Seven Network on Tuesday.
"If you get symptoms again, you need to assume it could be a new infection."
The Australian Health Protection Principal Committee has recommended the reinfection period be reduced from its current 12 weeks to 28 days, following the rise of cases of the BA.4 and BA.5 Omicron variant.
This means people will be required to get tested and isolate if they re-develop symptoms 28 days after recovering from the virus, and could be reported and managed as new cases.
NSW and Western Australia have already followed suit.
NSW Chief Health Officer Kerry Chant says the Omicron BA.4 and BA.5 subvariants are circulating widely in NSW.
"They are more able to evade immunity gained from previous infection and vaccination. Reinfection is more likely and possible just weeks after a prior infection," she said on Tuesday.
"We're urging people who have recently had COVID-19, even if they left isolation in the past four weeks, not to be complacent. If you develop symptoms again, make sure to test and isolate."
Prof Griffin said the rise in new COVID-19 infections alongside an increase in influenza cases was also concerning.
"This is translating into significant numbers in hospitals, with predictions ... we may exceed the hospitalisations we saw in the first big wave in January," he said.
"We cannot assume people are protected just because they've had COVID, you need to be up to date with your vaccines and linking with therapies if you are eligible."
This week, more people become became eligible for a fourth vaccine dose - or a second booster shot - as well as antiviral treatments to help offset symptoms.
Australians over 70 who test positive for the virus were from Monday offered access to antivirals on the Pharmaceutical Benefits Scheme.
Access was also expanded to people over 50 with two or more risk factors for severe disease, and Aboriginal or Torres Strait Islander people over 30 with two or more risk factors.
Anyone 18 or over and immunocompromised may also be eligible.
Normally costing more than $1000, the two antiviral treatments are now available for $6.80 for concession card holders and about $40 for everyone else.
LATEST 24-HOUR COVID-19 DATA:
NSW: 10,806 cases, 20 deaths, 2049 in hospital with 58 in ICU.
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