Bookings for all kids in that age group will open from September 13 following a green light from the national expert immunisation panel.

Prime Minister Scott Morrison said he envisaged the GP network being the primary source for child vaccination.

"That provides the opportunity for family vaccinations, for the family to get together across those age groups," he told reporters.

Pfizer jabs will initially be available through usual channels including GPs, pharmacists, federal vaccination centres and state-run hubs.

States and territories will be left to decide on whether to run school-based programs.

Mr Morrison encouraged parents to discuss vaccination with children and noted upcoming school holidays would be a good time for families to be immunised.

"We have some promising leads in terms of (securing more) doses. I can't confirm those at this point, but we've been working on them now for some time," he said.

"That is giving us some greater confidence about being able to particularly go forward with this decision to vaccinate children aged 12 to 15."

Chief Medical Officer Paul Kelly said more children were being infected in this year's outbreaks partly due to higher vaccination rates of adults.

"While the numbers are there and we are finding cases in children, most are in family clusters, some have been related to school clusters," he said.

"But almost entirely, the disease in children is much less severe than it is in adults."

Education Minister Alan Tudge said having all secondary-school aged children included in the rollout would disrupt transmission in schools.

About 260,000 children aged 12 to 15 with compromised immune systems, disabilities, underlying health condition or who are Indigenous were already eligible.

The extension to all people in that age group is expected to make a further 1.2 million eligible.

Mr Morrison chaired a national cabinet meeting with premiers and chief ministers which received a briefing about the rollout expansion.

Leaders also received updated modelling from the Doherty Institute which underpins a national agreement to reopen gradually when vaccine coverage reaches 70 and 80 per cent.

Mr Morrison has spent a week insisting the plan must be followed but struck a more flexible tone ahead of the meeting.

"When you get to 70 per cent and 80 per cent, sure, you've got to calibrate, you've got to fine tune," he said.

He flagged more discussion on ensuring the health system could cope with rising cases and deaths when restrictions are eased.

The institute argues it would be safe to open at the vaccine targets even if there are high case numbers in the hundreds.

But top-quality use of testing, tracing, isolating and quarantine needs to be maintained and small-scale lockdowns not ruled out even at the higher threshold.

NSW recorded another 882 new local infections on Friday, down from the previous day when the 1000-case barrier was broken for the first time in Australia during the pandemic.

Two more deaths took the national toll to 991.

There was 80 cases in Victoria and 21 in the ACT.

Australian Associated Press