The news comes as authorities investigate the death of a 48-year-old woman in NSW who reportedly received a COVID vaccination before developing blood clots.
Prime Minister Scott Morrison asked people not to jump to conclusions about the woman's death, as state and federal agencies gather further information.
Australians under the age of 50 were last week warned off receiving the AstraZeneca COVID vaccine, after a link was confirmed between the jab and rare blood clots.
The warning added to delays in Australia's vaccine rollout and made airlines' preparation for an October restart for overseas travel look optimistic.
The federal government's dumped timetable means Australia's border is unlikely to reopen until 2022.
Senior government minister Simon Birmingham said experts were still looking at how reopening could work in line with the vaccine rollout.
The vaccines reduce the risk of serious health consequences from coronavirus.
"What is less clear are questions around the extent to which the vaccines reduce the rates of transmission," Senator Birmingham told Sky News on Friday.
"So somebody who is vaccinated could still get COVID - the odds are they won't get sick - but could they pass it on to somebody else who may not have been vaccinated?
"Those questions and analysis around transmission are a live piece of work happening around the world at present."
Mr Morrison said Australians had become used to recording days of zero community transmission but that would need to change.
"If we were to lift the borders and people were to come, then you would see those cases increase," he told 6PR radio.
"Australians would have to become used to dealing with a thousand cases a week or more."
The government will also have to consider the possibility of Australians needing a third Pfizer jab, after the company's boss predicted that would be the case to maintain protection against the virus.
Mr Morrison said states and territories would need to get on the same page about acceptable virus levels when travel restarts. He continues to defend the vaccine rollout, rejecting comparisons with less developed nations at more advanced stages.
While mass vaccination centres are likely to administer the Pfizer and Novavax jabs later in the year, the prime minister rejected using major hubs to give doses of AstraZeneca to over-50s.
Despite doctors raising concerns about vaccine supply, Mr Morrison is adamant those issues have been largely solved.
Labor leader Anthony Albanese continues to criticise the government for its slow vaccine rollout, saying Australians stranded overseas should be home by now.
"This is a government that stands up for its own political interests," he told reporters in Brisbane.
"It's not on the side of Australians."
More than 1.3 million people have been vaccinated since the program started in February, with the government missing its own targets.