Vaccinating the majority of the adult population won’t be enough for a wholesale re-opening of international travel.

That is according to the chief medical officer of Australia who has been among those advising the UK government on tough new travel restrictions.

Professor Michael Kidd, acting chief medical officer at the Australian government Department of Health, said: “We don’t know how long it’s going to take before we move back to a degree of normality with travel.

“We would want to see a world where Covid-19 is much more under control.”

UK health secretary Matt Hancock acknowledged advice from “Australian colleagues” when announcing tough new restrictions on travel to Britain on Tuesday (February 9).

Hancock not only announced a new hotel quarantine regime for arrivals from high-risk countries, but a new Covid-test regime that will see all arrivals subject to two mandatory tests after arrival in addition to the pre-departure test already required.

He also unveiled severe penalties for flouting the rules, telling UK MPs: “We’ve been taking advice from our Australian Colleagues both at ministerial level and from leading authorities on quarantine.”

Speaking on a Capa Centre for Aviation webinar, Professor Kidd said: “Travel has been severely curtailed in Australia. Obviously, the vaccines are going to make a difference, but vaccine programmes are only just starting to roll out overseas.

“The roll-out to cover the entire adult population in Australia is expected to run until October and we still don’t have any vaccines licensed to be used in children.

“It means we’re unable to immunise a significant percentage of our population and a significant percentage of the people who will be on planes.”

Kidd argued: “We do know the vaccines prevent the development of serious disease and death from Covid-19, but there are a whole lot of things we don’t know.

“We don’t know if you’ve been vaccinated whether you can still be infected with Covid-19, be asymptomatic but still infecting other people. We don’t know how long the immunity from being vaccinated will last.”

Asked whether international travel could resume when most adults have been vaccinated, he said: “We still won’t have vaccinated the children so that is 25% of our population, and we don’t know what is going to be happening overseas.

“There are many countries where vaccination has not commenced and where there may be very large numbers of people who have not been vaccinated come October.”

Kidd insisted: “We would want to see a world where Covid-19 is much more under control. It may well be we start on a country-by-country basis rather than opening up to the entire world.

“It may well be many of the health precautions we have in place will still be required – wearing masks, hand hygiene, physical distancing.”

He said it may also “depend on which vaccines have been used in countries, and which variants are circulating.

“For example, we have the Sinovac vaccine being used in China and rolling out in a number of other countries. The Sputnik V vaccine has been rolling out in Russia and is also being used in other countries.  There is still a lot to learn as we see how populations respond to these vaccines.

“We’ll learn more about each new variant as they appear. That is obviously what our quarantine system is set up to do.”

Australia has a 14-day quarantine system in place for arrivals and Kidd said: “I don’t see it coming down.”

Kidd added: “I hope I’m wrong. I hope things improve dramatically over the months ahead.

“We need to watch and wait, see what is happening overseas and be continually ready to update our plans in light of what happens.”