The era of risk-free travel will never return, even with the advent of a COVID-19 vaccine, experts say, and the stop-and-start nature of domestic travel in Australia foreshadows what the future of international travel will be like.
When Qantas chief Alan Joyce predicted recently that international air travel wouldn't resume until mid-2021 due to the impact of COVID-19, it wasn't the forecast of some epidemiological seer, but rather an educated guess.
Indeed, predicting a date for the resumption of overseas travel has become one of the world's biggest and most imperfect guessing games. And the answer will assist nations emerging from economic oblivion, with tourism and travel estimated to be worth almost $US3 trillion to the global economy.
The difficulties in restarting domestic travel, with the Northern Territory the latest to baulk at fully reopening its borders, has provided an insight into just how difficult it will be for international tourism to recommence, even with the advent of a vaccine.
It will be particularly the case for those nations that are seen to have managed COVID-19 well - they now effectively have the most at stake. Even the vaunted travel bubble between Australia, New Zealand and Pacific nations has failed to inflate, with no clear date for its introduction in sight.
"There are a lot of arbitrary restart dates," says Adam Kamradt-Scott, a University of Sydney associate professor who specialises in global health security and international relations, "and that simply reflects the fact there remains so much uncertainty.
"You might even describe it as pervasive uncertainty, as countries are still coming to grips with dealing with the first wave of COVID-19 infections and we remain unclear as to when or if a vaccine will become available."
Understandably, hope is focused almost exclusively on a vaccine. But even if one or more are developed, it may not represent the panacea that the tourism and aviation industries and, for that matter, inveterate travellers, are expecting.
Experts point to myriad obstacles such as the fact that they will not be 100 per cent effective (no vaccine has even been so with Jonas Salk's 1955 polio vaccine coming the closest).
Add to that the real potential for the take-up rate to be low in countries like the United States where, according to a poll reported in The New York Times, only 50 per cent of people would be willing to be vaccinated. There's also the possibility that rich countries could monopolise vaccine and treatment supplies.
"The idea that the behaviour that we've just seen from the US - whereby they sought to buy up all the supply of a drug that helps treat COVID-19 - would not be repeated when we see a vaccine emerge would be short-sighted, even naive," Dr Kamradt-Scott says.
He believes the next 12 to 18 months will see a lot of travel disruption due to new clusters or small outbreaks forming, as evidenced by the recent Victoria outbreak. Airlines or countries may also choose to refuse entry to international travellers who decline to be tested.
"When a vaccine does become available, and we obviously are hopeful one will, I suspect we will see new documentation requirements confirming that travellers have been vaccinated, in a similar way to what we seen with yellow fever," he said.
"In the event travellers haven't been vaccinated, individuals would be likely be given the choice of then being vaccinated or returned to their point of origin. Equally, airlines may start requiring evidence of vaccination before they permit travellers to board, particularly if governments insist the cost of returning unvaccinated travellers be met by the airlines."
But Sara Davies, a specialist in global health governance at Queensland's Griffith University, says that even proof of immunisation may be an imperfect measure, due to the potential for fake immunisation certificates to be created.
"Fraudulent claims of vaccination will be a legitimate concern, as will anti-vaccination populations and even those who are not anti-vaccination minded, but may be immune compromised and can't be vaccinated."
When international travel does resume for Australians it will almost certainly involve Asian countries such as Singapore, South Korea, Japan, Taiwan and perhaps even China, all nations which, despite their ups and downs on the coronavirus curve, have performed well in the pandemic compared to the US and the UK.
But Australian authorities will want to be sure of the integrity of such bubbles and those who are part of them, lest travellers return home with COVID-19 as well as souvenirs from their holiday or business trip.
"We saw this issue emerge in the February-March period before lockdown where individuals from travel-banned locations re-routed to make sure they could arrive in Australia," says Dr Davies.
"The question of who will be responsible for ensuring a person is not transiting from outside the bubble will need to be established because it will be costly and time consuming.
"Is it Australia as a destination state, or, say, Singapore as a transit state that has to take responsibility when an individual has tried to enter from a banned location? Heavy fines and payment for accommodation could be introduced to make sure this doesn't happen."
Marylouise McLaws, an epidemiologist specialising in infection prevention and control at the University of NSW, agrees that when international travel does resume for Australians beyond Oceania it will likely be focused on a group of countries in Asia where COVID-19 has been well-managed and which can reached in a single flight.
"The idea of having risk-free travel is really a pre-COVID-19 concept," says Professor McLaws, "that may take many years to achieve again."