Federal Health Minister Mark Butler says the Therapeutic Goods Administration is considering an application from drug maker Moderna to allow its vaccines to be given to children aged from six months to five years old.

"If it is approved by the TGA that will then go to our advisory group on vaccines to consider the way in which this should be rolled out to the community, so I'd expect it to be a matter of some weeks," Mr Butler told reporters in Canberra on Tuesday.

Earlier, he told ABC radio, it would be "unthinkable" not to hold a royal commission into the nation's pandemic response.

"The amount of money spent, the death, the dislocation. We know a very long tail of mental and physical distress will be coming our way over the next couple of years," he said.

"It would be unthinkable not to have a very deep look at how we responded to that and learn the lessons."

He said any inquiry needed to be carried out over the next three years.

Meanwhile, Australians will have access to a single vaccine for COVID-19 and influenza by 2024 as clinical trials are set to begin.

The combined shot for flu, COVID-19 and respiratory virus RSV was in the early testing stages, with trials to start later this year, Moderna chief medical officer Paul Burton said.

Dr Burton expects combined vaccines will be key to fighting respiratory diseases in the aftermath of the pandemic, and to adapting to multiple strains within one season.

He said bringing vaccines together and adapting would be the future as the world considered diseases other than COVID-19.

Meanwhile, Australia's multibillion-dollar mRNA manufacturing hub will be bigger than initially expected.

The first of its kind in the southern hemisphere, the facility was announced in March by the Morrison government as part of an agreement with Moderna.

Finding a location had reached its final stages and a site would be announced in a few weeks, Moderna Australia general manager Michael Azrak said.

"It's taken a little bit longer than we anticipated because we're actually going to be building a larger facility than we anticipated," he told Sky News.

The pharmaceutical giant aimed to break ground on the Victorian site before the end of the year, Mr Azrak said.

It will be operating by the end of 2024, subject to approval by the medicines regulator.

LATEST 24-HOUR COVID-19 DATA:

NSW: 7805 cases, seven deaths, 1499 in hospital with 57 in ICU

Victoria: 7507 cases, 28 deaths, 434 in hospital with 21 in ICU

Queensland: 4797 cases, four deaths, 491 in hospital with seven in ICU

NT: 232 cases, no deaths, 17 in hospital with none in ICU

Tasmania: 1001 cases, no deaths, 41 in hospital with two in ICU

WA: 4885 cases, six deaths, 259 in hospital with eight in ICU

SA: 2270 cases, 11 deaths, 230 in hospital with nine in ICU

Australian Associated Press