The airline had planned to begin regular international flights from the end of October, but has pushed it back to the end of December.
This is in light of the Federal Government revising its anticipated timeline for Australia's vaccine rollout, which has been far slower than forecast.
Consequently, an anticipated wider reopening of international borders has been pushed back even further.
"We remain optimistic that additional bubbles will open once Australia's vaccine rollout is complete to countries who, by then, are in a similar position, but it's difficult to predict which ones at this stage," a Qantas spokesperson said in a statement.
"We will keep reviewing these plans as we move towards December and circumstances evolve."
The same statement touted Qantas' "critical repatriation and freight flights" as well as domestic and trans-Tasman flights.
"We will reach out directly to any customers with a booking between 31 October 2021 and 19 December 2021, however recent levels of uncertainty meant international booking levels were relatively low," the spokesperson said.
"Again, please note that trans-Tasman flights are unaffected."
Qantas has urged customers to wait for the airline to contact them, because of a high volume of calls to their contact centre.
Just 10 per cent of Australians have received a coronavirus vaccine dose so far, with most of those having got just the first dose.
By contrast, more than a third of Americans have been fully vaccinated.