The border has been closed to non-residents for more than one year, with strict limits in place for returning Australians which has resulted in tens of thousands stuck abroad.

Chief Medical Officer Paul Kelly said the border closure has protected the island nation from the severity of the pandemic seen in other countries.

"The opening of the international border will be a difficult moment," Professor Kelly has told a Senate estimates hearing in Canberra on Wednesday.

"It will be a very different change to where we are and have been throughout the last year in relation to this pandemic.

"We have had very few cases this year - except for those in hotel quarantine - but that will be a very difficult decision to open the border."

Prof Kelly said he recognised the border closure has caused a lot of strife, particularly to businesses reliant on international tourism.

But he said it was a complex issue in regards to linking the coronavirus vaccine rollout to easing restrictions and ultimately the border.

No date has been given for reopening Australia.

Arrivals currently have to undertake 14 days in hotel quarantine after landing in Australia.

The quarantine system is the biggest risk of the virus to Australia and leaks from hotels have caused multiple outbreaks.

With low case numbers this year, Prof Kelly said it was important to remember a global pandemic was still occurring.

"Everyone outside of our borders at the moment are suffering in various ways."

Australian Associated Press