Prime Minister Scott Morrison said the federal government would be keeping a close watch on the rates of serious illness in coming months.
Mr Morrison, who is returning from a trip to the UK and France, said hospitalisations were rising in Britain despite high vaccination rates.
"If the virus is there but the hospitalisations and the serious illness don't occur and we see that on a sustained basis, well that says there is a potentially different pathway there," he said.
However, Australia is also working with Singapore on another potential travel bubble, once vaccination rates are higher.
In contrast, major European nations are reporting high vaccination rates with the United Kingdom having administered two doses to almost 58 per cent of adults.
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