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 is in early testing stages with trials to start later this year, Moderna chief medical officer Paul Burton says.

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

“We still have to be cautious, this fight is not over and we can’t let our guard down,” he told Sky News on Monday.

Mr Burton said bringing vaccines together and adapting will be the future, as we think about diseases other than COVID-19.

Meanwhile, Australia’s multi-billion dollar mRNA manufacturing hub will be bigger than initially expected.