Modelling from the Medical Journal of Australia shows the current mixed vaccination program will not be enough to protect the entire populous against COVID-19, until younger children between five and 16 can be fully vaccinated.

The data from MJA is based on the entire population rather the Doherty Institute modelling, which is based on 70 to 80 per cent inoculation rates of the adult population needed before lockdowns and state border closures can be eased.

MJA's revelation comes as the ACT government, from Monday onwards, begins prioritising year 12 students for Pfizer jabs to ensure exams can be conducted in physical classrooms.

The James Cook University and Monash University report found vaccinating high-risk transmitters, such as children and younger people, would be a priority once most of the population had received two COVID-19 vaccines.

JCU infectious disease expert Emma McBryde said without vaccinating children between the ages of five and 15, the total population would only reach a herd immunity of about 60 to 70 per cent.

"Vaccinating the vulnerable first is the optimal policy at low coverage, but vaccinating high transmitters becomes more important in settings where reproduction numbers are lower and coverage is higher," Ms McBryde said.

"Australia is unlikely to achieve herd protection unless vaccination is extended to younger ages or combined with other measures.

"Australia should now prioritise delivering Pfizer vaccine to 12 to 40 year-olds."

MORE COVID-19 NEWS:

Ms McBryde said the research was intended to show the need for governments and health authorities to explore a range of vaccine strategies to ensure a majority of the population was protected from the worst effects of the disease.

Vaccination policy among younger children has become a heated debate with some states and territories flagging re-openings would not occur until children were eligible for immunisations.

Queensland Premier Annastacia Palaszczuk has faced criticism from the Morrison government for saying the state's border would remain closed until children were fully vaccinated.

The splintering of the national plan has also embroiled Western Australia and Tasmania, which have also flagged hesitation to reopen while case numbers surge in COVID-plagued states.

ATAGI and the federal government have approved Pfizer shots in children as young as 12 years old, however Home Affairs minister Karen Andrews, who took a swipe at the Queensland premier last Friday said no jurisdiction in the world had mandated vaccines for younger children.

Ms Palaszczuk has also been condemned for exaggerating Doherty figures, claiming once targets are reached, 80 people a day would still die from COVID-19.

The debate over children being eligible for a shot has also coincided with new figures showing the ACT is leading the country in the number of people who have received two doses of either vaccine.

The nearly 50 per cent of the Canberra population being vaccinated is in despite of 15 new cases being recorded in the 24 hours to Saturday at 8pm.

Meanwhile, federal minister Stuart Robert has left the door open to changing the national COVID-19 reopening plan amid growing reservations from state and territory leaders.

The close ally of the Prime Minister says the plan, which proposes that coronavirus restrictions ease once vaccination rates hit 70 and 80 per cent, is regarded as a guide that may need to be altered if circumstances change.

Asked on the ABC's Insiders program if the 80 per cent threshold might shift if there is worry about hospitals coping with COVID, Mr Robert responded with: "Goodness, anything could change next week."

"Well, of course plans change," he said. "Come on, nothing's set in stone. My goodness."

"Look at the last 12 months, things have been shifting on a daily and weekly basis. A plan is always a basis for change, it has to be."

So far, more than 35 per cent of the eligible Australian population aged over 16 are fully vaccinated with two doses.

Mr Robert said lockdown decisions were for premiers, but the national plan would provide guidance.

"At 80 per cent mark, you would be questioning why there are lockdowns," he said on Sunday.

ACT Chief Minister Andrew Barr said Mr Robert appeared to have "read the national plan".

"Even just a cursory glance at the one page document that constitutes the national plan does say that it is based on the current situation and subject to change," Mr Barr said.

Deputy Labor leader Richard Marles said it was important that the national plan was supported, but felt premiers had legitimate questions about children. "What's important is that the federal government is working with the states to bring them along," Mr Marles told Sky News' Sunday Agenda program.

- with Karen Barlow

Our coverage of the health and safety aspects of this outbreak of COVID-19 in the ACT and the lockdown is free for anyone to access. However, we depend on subscription revenue to support our journalism. If you are able, please subscribe here. If you are already a subscriber, thank you for your support. You can also sign up for our newsletters for regular updates.