Australian Medical Association president Omar Khorshid told a Senate inquiry on Tuesday a rollout for younger children would depend on clinical trials and regulatory approval.

"A school-based vaccination program next year [would] be my guess, because it will take that long for the various approvals to come through," he said.

"And of course, we need to have vaccine supply. If that coincides with the school holidays, there won't be an ability to easily stand up a school vaccination program."

Nine people under 18 have been hospitalised in the ACT with COVID-19 since the outbreak began, including 6 aged under 12.

Of the 641 total cases in the outbreak, 31 per cent (189) were under 18, and 17 per cent were aged under 12.

MORE COVID-19 NEWS:

Dr Khorshid said there were "mixed reports" over whether Delta was more serious than other variants in children, but conceded it was significantly more transmissible.

"Children are at very low risk of becoming seriously ill due to COVID-19 ... all around the world we're seeing very low rates of hospitalisation in children," he said.

Dr Khorshid said the risk of "long COVID" - a condition lingering well after the virus - was much lower in children though "clearly not zero".

"Also, the risk of long COVID does appear to be much lower in children than in adults, but clearly not zero."

Despite positive noises from Pfizer, he said Australia needed to "wait for the science to come in" on vaccinating children, who he argued could be protected through a number of risk mitigation strategies.

"We've got to be very careful about weighing the risks and benefits of vaccination up in each individual age group, rather than applying a broad brush to all children," he said.

Pfizer has signalled it will seek regulatory approval in the US, Europe and elsewhere for its shot to be used on children aged five to 11 after promising clinical trial results.

Health Minister Greg Hunt wrote to Pfizer's Australian managing director Anne Harris, inviting the company to submit an application to Australia's Therapeutic Goods Administration.

Australia's expert immunisation panel ATAGI would also have to approve vaccines for younger children.

Deaths of unvaccinated children should not be discounted, paediatrician Dr Greg Kelly told the hearing.

Even if only 2 per cent of children are hospitalised with Covid - it's currently 4 per cent in the ACT - with vast numbers of children becoming infected, deaths were inevitable, he said.

"When we have 5 million children in Australia, 29 [deaths in six months] doesn't necessarily sound like a lot, but it is twice the number of children we expect to die from drowning and twice the number of children we expect to die from road traffic accidents in that time."

Epidemiologist Mary-Louise McLaws said people aged under 40 would be more susceptible to Delta outbreaks if restrictions lift at 70 and 80 per cent double-dose thresholds.

"All the younger groups are at risk," she told the hearing.

"I would ask the government to reconsider and not open immediately until that group gets double dosed, and it should be done rapidly."

Latest figures show more than 14 per cent of children aged between 12 and 15 have received a first dose of a COVID vaccine.

UNSW epidemiologist Raina MacIntyre said not immunising enough young people would lead to increased pressure on already strained hospital systems.

"When any vaccine program targets a particular age groups, it shifts the disease burden into a younger age group," Dr MacIntyre said.

"We've seen with COVID in other countries where it has become a disease of kids and school outbreaks and paediatric intensive care units full."

With AAP

Our journalists work hard to provide local, up-to-date news to the community. This is how you can continue to access our trusted content: