Pre-flight testing is required for people coming into Australia, but UNSW epidemiologist Mary-Louise McLaws doesn't think it's enough.
"They often have it several days before they hop on the plane," she told the Nine Network on Wednesday.
"Anything can happen between that three day period of having the PCR (test)."
"Then also they may have to transit. They may, of course, inadvertently acquire it there. It's just an additive bundle of prevention."
Australia is on the cusp of having 80 per cent of people aged 16 and older fully vaccinated.
The latest federal data shows 78 per cent are double-dosed, with about 88 per cent partially vaccinated.
NSW has fully vaccinated 88 per cent of its over-16 population as the state accelerates the further easing of restrictions for the double-dosed.
It recorded 173 new cases and four additional deaths on Tuesday.
Victoria surpassed an 81 per cent double-dose rate as its daily infections fell below 1000 for the first time since September.
It reported 989 new infections and nine more deaths, and the ACT eight additional cases.
The national capital has fully vaccinated more than 93 per cent of residents aged 12 and older.
The Northern Territory and Western Australia are Australia's least vaccinated jurisdictions.
Just under 64 per cent people in WA and the NT are double-dosed. Queensland is slightly ahead, with a vaccination rate of nearly 65 per cent.
Pressure has been mounting on states with no infections or low numbers of cases to lift vaccination rates so internal borders can reopen further.
Meanwhile, US manufacturer Novavax has asked the Therapeutic Goods Administration to give its jab the green light.
Should it be approved, Novavax will be the fourth COVID-19 vaccine made available in Australia.
The government has purchased more than 50 million doses expected to form part of its booster shot rollout starting with aged and disability care residents.
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