Australia's Chief Medical Officer has warned the Omicron variant of COVID-19 could see changes in terms of severity, transmission and vaccine efficacy.
Professor Paul Kelly said Omicron was "a variant of concern" during an interview with Michael Rowland on ABC News Breakfast on Monday.
"Why are we concerned? Firstly, genetically, there are quite a few changes to this. I will stress, that it's still the same SARS-CoV-2 that we've become used to, but it is different from previous versions," he said.
"There are suggestions from that genetic variation that there could be changes in severity, transmissibility or indeed, interference the efficacy of vaccines and treatments."
Professor Kelly said the Omicron variant could actually be "relatively mild compared with previous versions" such as the Delta strain.
"It is early days and we need to be careful of that. But there's no sign that it is more severe at the moment," he said.
However the CMO warned the latest variant "will spread" because it was highly transmissible.
"It does transmit from person-to-person quite readily - at least at well as the Delta virus," he said.
Professor Kelly said "there is no solid evidence" that Omicron could effect the efficacy of vaccines but said Australia was "well placed" to adapt its vaccines if need be.
"It is one of the major technological and scientific advantages that has happened from this pandemic, that mRNA platform can be changed very quickly," he said.
"Moderna, for example, put out a press release on the very next morning after the variant was said to be of concern, to say that they were working on a specific vaccine for that variant.
"And the other ones also, AstraZeneca, can change the make-up of the vaccine very quickly. So we are well placed, if that was to be the case. But I would stress at the moment that there is no evidence that that would actually be necessary."
Australia shut its borders to nine southern African countries and suspended all flights from the region amid concerns about the Omicron variant on the weekend, which Professor Kelly said was "swift and proportionate action".
When asked if Australia would close its international borders to all countries once again, Professor Kelly said it is "ultimately is a decision for the national Government".
"They listen. I've already spoken to the Prime Minister and the [health] minister this morning and we've been talking several times over the weekend and I'll continue to give that advice," Professor Kelly said.
The CMO said banning the southern African countries had "bought time" in deciding whether mandatory 14-day hotel quarantine would also be brought back.
"We're taking a risk-balanced approach at the moment and concentrating on those nine southern African countries," Professor Kelly said.
"We have increased our surveillance at the border, and after the border, we're working very closely with our colleagues in New South Wales and Victoria, particularly, because they're the ones that have had quarantine-free travel, as well as in the ACT, as to what is the best approach.
"At the moment, we've bought time to get more information and to consider that balance, but there's always pros and cons for these sorts of decisions. That's what we're doing at the moment."