With almost 60 per cent of Australian children aged 12 to 15 now fully vaccinated against COVID-19, the focus is turning to younger age groups.

This week Israel followed the United States in clearing the Pfizer vaccine for use in those aged between five and 11.

Australia's medical regulator, the TGA, is watching those countries closely, but Health Minister Greg Hunt has said it's unlikely younger kids here will get the vaccine before Christmas. 

While the Pfizer vaccine has been used both safely and effectively in adults, approving it for our youngest citizens is more complex.

First things first, why are we vaccinating kids?

Just like giving the green light to vaccines for older Australians, approving it for younger ones involves a calculation of benefit compared to risk.

Kids tend to be less severely affected by the COVID-19 virus, so even a very small number of adverse reactions during clinical trials could make it harder for health authorities to justify the value of a vaccine dose.

But a very small number of children who become infected will become severely unwell. Infections in unvaccinated children have also risen due to the highly infectious Delta variant.

As of November 16, there had been a total of almost 27,000 cases in Australia among children aged zero to nine, and data from the first eight months of this year shows 2.5 per cent of them were hospitalised. 

In the UK, about 10 per cent of children aged two to 11 reported at least one lingering symptom, five weeks after a positive diagnosis. 

While children under 12 remain unvaccinated, they could also potentially spread the virus to others — particularly vulnerable people.

Which vaccines could kids potentially get?

When the rollout is expanded to include younger children, they'll be getting Pfizer or Moderna shots. 

Both mRNA COVID-19 vaccines have already been approved for use for kids aged 12-15 and both pharmaceutical companies have applied to use their vaccines on younger children.

Clinical trial data from the US has been promising, with Pfizer saying its vaccine showed 90.7 per cent efficacy against coronavirus in a clinical trial of children aged five to 11.

On Sunday Mr Hunt noted the trial had far fewer participants than the adult COVID-19 vaccine trials, as it was initially limited to 2,268 children.

He said the government's expert immunisation advisory body, the Australian Technical Advisory Group (ATAGI) was waiting for more information before making its decision.

"They want to review the real-world data coming out of the United States," he said.

Are vaccines safe for kids? 

The US medical regulator, the Food and Drug Administration (FDA), has said the benefits of the Pfizer vaccine "clearly outweigh" the risks for children aged five to 11.

None of the children aged five to 11 in Pfizer's clinical trials experienced the rare heart inflammation side effects known as myocarditis and pericarditis, which have been linked with the mRNA vaccines in very rare cases, particularly in young men.

FDA experts came to the conclusion that even if younger age groups recorded similar numbers of cases of myocarditis as 12- to 15-year-olds, the risk of being hospitalised from COVID-19 was still greater.

Moderna says early trial data for children six to 11 shows its vaccine is also safe and effective. 

Are we ready to vaccinate younger kids?

The government says it's poised and ready to roll out the Pfizer vaccine for under-12s, once its experts give it the green light. 

The TGA is still evaluating what dose is required, with the Health Department saying that evaluation is being undertaken "as a priority".

But it's likely Australia will fall in line with the US and Israel, and authorise a 10-microgram dose of Pfizer for children in the younger age group, which is one third of the dose given to those aged 12 and older.

In the US, paediatric vials have different doses, dilution requirements and storage conditions than those available for teens and adults. 

The Health Department says Australia has already bought some of these vials as part of its contract with Pfizer. 

The man charged with overseeing the vaccine rollout, Lieutenant General John Frewen, recently told Nine Newspapers that while a rollout of shots to kids through schools was possible, GPs, pharmacists and mass-vaccination hubs would likely inoculate most children. 

What's the next step?

Assuming the TGA approves the Pfizer vaccine for children aged five to 11, ATAGI will then make its own assessment. 

Mr Hunt says he believes that'll happen in January next year. 

Shadow Health Minister Mark Butler has called for more details, saying Australians need to know exactly how many vaccine doses the government has secured for the youngest members of its population. 

"Greg Hunt keeps assuring us that we have contracted supply for that, but we know with overseas experience that they are different vials, there will be competition around the world for those vials and we need some clear answers for parents from Greg Hunt," he said on Tuesday.

"When will those vials start arriving on Australian shores to be able to be provided and supplied to Australian children, provided of course that they get the proper approvals?"

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