Director of Victoria University's Mitchell Institute Max De Courten said infants will soon become the most at risk of being exposed to COVID once medical regulators sign off on vaccines for five to 11-year-olds.

He foreshadowed children aged between zero and five would be most in danger of infection and large numbers of childcare centres would be exposure sites.

"The virus is moving towards the unvaccinated and once we have a vaccine for young children aged five to 11, basically the very young ones from zero to five will be making up 40 per cent of the unvaccinated in Australia," he told Sky News on Thursday.

"The early childcare sector is the next front line, but that's related to the great vaccine success in older age groups."

It comes as Health Minister Greg Hunt said a decision by the Therapeutic Goods Administration was imminent in approving the Pfizer vaccine for five to 11-year-olds in Australia.

The decision would follow moves made by US regulators earlier this week to approve the vaccine for the age group, which will allow for as many as 28 million American children to be vaccinated.

"(The TGA) will work through that. They will consider all of the data. They will work as quickly as possible," Mr Hunt said.

"They've done all the work to ensure that it's safe and effective, we have the doses, we have the distribution system."

The minister said more than 100,000 Australians have received booster shots since the medicines regulator approved the Pfizer top-up for the general public last week.

Mr Hunt said a second booster could soon be before the TGA for approval, with Moderna indicating they were about to submit their application.

"The booster program is ahead of expectations, and Australians are stepping forward and doing their bit," Mr Hunt told reporters in Melbourne.

"When (the TGA) have done their assessment and made their findings and found it to be safe, then (Moderna) will be added to the list of boosters."

The latest national vaccine figures have shown 79.1 per cent of over 16s are fully vaccinated and 88.9 per cent have received one dose.

There were more than 181,000 vaccines administered on Wednesday.

It comes as Australia's most populous states recorded a spike in the number of new infections on Thursday.

Victoria reported 1247 more cases and nine additional deaths, following two consecutive days of new infections numbering below 1000.

NSW recorded 308 more cases, an uptick compared with recent days where new infections have come in below 200. There were also four more deaths.

Queensland registered three new cases in the state on Thursday, while there were 13 new infections in the ACT.

Australian Associated Press