However, Professor Peter Collignon from Australian National University said the risk of transmission between New South Wales and New Zealand was very low.
"With a population of about 5 million, there can't be that many people out in the community at the moment that have got it. Let's say worst case scenario, I'd assume there's four or five. It still means any one individual has less than a one in a million chance of having the virus at this point of time," he said.
"There must be a very low risk of anybody being in Sydney going back to New Zealand or anywhere else, of actually carrying the virus ... to put this in perspective, there's been people coming from overseas often, they've had a 1 or 2 per cent chance of carrying the virus if they come back from the US or Europe for instance and slightly higher at the moment from India."
He said authorities and the community would need to eventually have a discussion on what level of risk was worth taking.
"My view is, we're going to have this problem for another couple of years, even after vaccination of most of the population ... we're going to still have this risk that the virus can transmit because the vaccines don't give you 100 per cent protection," Collignon said.
"So at some stage, we're going to have to work out the level of risk we're willing to take. The more people are vaccinated, the more risk we can afford to take, because even if it does escape, there'll be less consequences, particularly to people over the age of 70, who are most of the people that died."
Collignon said considering the current risk level, he would not have closed travel with New South Wales over the new community cases.
"At a level of one in a million, I would think that's too low level of a risk to draw it all up, so to speak, but if there were a lot more cases then there is an argument to stopping people travelling freely until we get a lot more people vaccinated.
"I would actually think if we're not finding any more cases in New South Wales, then particularly if there's no more community cases where we don't know the source, yes I think it would be worth firing it up again, because I think that actually means the level of risk is very very low."