A fourth COVID vaccine dose should be offered to all Australians over 50 as a way to reduce the risk from rising virus infections across the country, an epidemiologist says.

As Australia's death toll from the pandemic surpassed 10,000, infectious diseases paediatrician Professor Robert Booy said lowering the age limit for a fourth vaccine dose - or second booster - should be considered.

Currently, a fourth dose is only available to those over 65, those in aged or disability care, as well as people who are severely immunocompromised.

"Getting the lower limit from 65 down to 50 is a good idea," Prof Booy told Sky News on Monday.

"There's a lot of people with chronic medical conditions in their 50s and early 60s, and they would really benefit."

Prof Booy said about 20 per cent of the eligible population over 65 had yet to receive their fourth dose.

"They're playing roulette ... there's an effective vaccine. If you had three doses, the fourth will dramatically increase your protection," he said.

"Having a booster some time in the last six months is very protective against hospitalisation and death."

As COVID cases continue to rise across Australia due to more transmissible strains of the Omicron variant, experts have called for a reintroduction of mask mandates in a bid to mitigate the spread.

Professor Adrian Esterman said caution was needed as public health restrictions were eased.

"At the moment we are getting the BA.5 and BA.4 variants taking over from BA.2," Prof Esterman told ABC TV on Monday.

"We are seeing the effective reproduction number - which tells us how bad or good things are going - greater than one in all states and territories.

"And that tells us that case numbers will be going up, hospitalisations will invariably go up ... and deaths will go up as well."

However, epidemiology chair at Deakin University Catherine Bennett said while mask use should be increased, mandates weren't the way to do it.

"When you have rules in place they start to wear out peoples' compliance or adherence to those rules, and the enforcement of those rules. We've seen that happen," she told Melbourne radio station 3AW.

"Helping people to understand their risks relative to where they are, I think, can also make a difference."

Health authorities have urged almost six million Australians to get vaccine boosters to ease pressure on hospitals and ensure greater personal protection from the virus.

It comes as border restrictions enforced in response to the virus are due to be dropped, with arriving passengers no longer required to declare their vaccination status or obtain a travel exemption.

Changes to the Biosecurity Act coming into effect on Wednesday were made following advice from the Chief Medical Officer Paul Kelly that it was no longer necessary for travellers to declare their vaccination status.

The Digital Passenger Declaration required people entering Australia to provide their contact details as well as declare their vaccination status, where they had been in the past 14 days, and commit to following quarantine and testing requirements.

LATEST 24-HOUR COVID-19 DATA:

NSW: 8958 cases, one death, 1725 in hospital, 50 in ICU

Victoria: 7317 cases, 24 deaths, 513 in hospital, 28 in ICU

Tasmania: 1094 cases, no deaths, 72 in hospital, three in ICU