Flu season is likely to hit Australia later than usual this year, and it could make a big comeback.

Australia saw the lowest number of influenza cases on record in 2020, and there have been few cases recorded over the past six months, following a record-high number in 2019.

So how will things play out in 2021?

"That's the $64 million question," Ian Barr, from the WHO Collaborating Centre for Reference and Research on Influenza, told AAP.

"It will remain low but when things free up, when international borders reopen, there is a much greater chance for circulation.

"While we might not see flu in the normal season it might be delayed and come back strongly," he said.

Australia's normal flu season runs from June until September or October.

The global circulation of the flu is well down for 2021 so far, but there have been outbreaks in East Timor, Cambodia, Bangladesh, Laos, India and Vietnam.

Chris Moy from the Australian Medical Association says high immunisation rates, as well as mask-wearing and physical distancing due to COVID-19, helped stop the spread of flu last year.

"The same things that reduce COVID reduce the flu as well," he told AAP.

It's estimated these measures prevented about 2800 influenza deaths.

But Dr Moy said a year with very little flu can often mean a reduced immunity in the population, resulting in a big flu season the following year.

Doctors are "scrambling" to administer regular flu shots at around the same time as the COVID-19 vaccine rollout, he said.

The two vaccines should be administered 14 days apart, so that any adverse reactions can be attributed to the correct medication and treated accordingly.

"If you had both of them you wouldn't know whether you were Arthur or Martha," Dr Moy said.

Prof Barr said people who already have a date to receive a COVID vaccine should plan their flu jab around that date.

There are two types of flu shots available this season, the standard shot and a high dose for people over 65, available only through GP clinics.