This is an exciting development. This research further underscores the safety and efficacy of the Pfizer COVID-19 vaccine for children, which is one third the adult dose. We can see in the case of the United States there will soon be wide-spread vaccinations for children between the ages of 5-11. We should move promptly here in Australia to extend the same protections to children under the age of 12.

The new study from Pfizer is important because it shows the safety and efficacy of the vaccine, despite the small numbers in the trial.

Importantly though, because only 1500 children received the Pfizer vaccine, the data on safety with regard to rare side effects is inadequate.

We need real-world information on 1000 times as many children (one to 2 million) to be properly reassured that young children do not experience rare but important serious side effects like myocarditis and pericarditis.

We know the incidence of myocarditis after mRNA vaccines is higher after the second dose than the first, higher in boys than in girls, and higher in teenagers than in young adults. There remains the real possibility that children aged five to 11 could have an even higher risk of myocarditis, despite the fact that only a 1/3 dose has been used in this study.

We do not know the underlying biological processes causing myocarditis in children following an mRNA vaccine and we do not know if these are dose related or not. More real world evidence must be collected to give us adequate reassurance, about the safety of this vaccine in large numbers of young children.

The Australian and New Zealand Paediatric Infectious Diseases Group (ANZPID) supports the Therapeutic Goods Administration (TGA) and the Australian Technical Advisory Group on Immunisation (ATAGI) in their careful consideration of COVID vaccinations for 5- to 11-year-olds for the known benefits, risks and uncertainties, as they do for any new vaccine and program.

The US has provided Emergency Use Authorisation for this vaccine from 5- to 11-year-olds for their context. Soon millions of children will be vaccinated. As such, additional safety data on any rare side effects will become available. Whilst we await the TGA and ATAGI decisions in Australia, other measures remain helpful to protect children from COVID and ensure education, social engagement and their wellbeing are optimised.

Although at first glance the numbers may seem alarming for 5- to 11-year-olds – more than 7,000 cases and 244 admissions in Australian children from January - October 2021 – these do not form a complete picture of COVID in children. Many cases in children are asymptomatic, some are likely to be undiagnosed, and a large proportion of hospital admissions are because of sick parents being unable to care for their children. Very few children have required specific antiviral or other treatments and a very small proportion (less than 1 in 3000 cases) have required intensive care. There have been no deaths among 5- to 11-year-old children, but sadly two adolescents have died with COVID in Australia.

The main impact of COVID on children is less about the direct consequences of infection, as COVID is generally a mild illness, but more the indirect impacts through a lack of face-to-face teaching, sporting and social activities.

The evaluation of the safety, immunogenicity and efficacy of the Pfizer BNT162b2 vaccine in very young children needs to be considered very carefully. Responses in phase two trial results for children aged 5 to 11 years will be significantly different to those seen in adults especially the earlier ages where the immune system is immature and still developing.

While no vaccine related serious adverse events were reported over the time frame investigated in the current study, longer term responses will need to be considered with caution. It is encouraging that neutralising titres of antibodies were generated but this must be balanced against the higher risks associated with vaccination in this age group.

Children who contract COVID-19 generally have mild or asymptomatic infections (DOI.org/10.1038/s41467-020-19545-8) with early studies indicating that the innate immune system protects the very young against severe COVID-19. Based on these findings some consideration must be made as to whether the risks associated with vaccination out weight concerns with COVID-19 infection in this group.

In adults the precise antibody titre required to prevent severe infection has not yet been determined (i.e. correlate of protection) and we are now moving to booster vaccination. One wonders if this will also inevitably be extended to very young children before the associated risks are considered more carefully.

This is an important study and necessary for any roll out of the Pfizer vaccine to children less than 12 years old. Of note a lower (1/3 of a dose) antigen vaccine elicited antibody responses similar to younger adults. The authors report the vaccine had a "favourable safety profile" and no serious adverse events were reported.

It is important to note that this is a small study with only 1517 children receiving active vaccine and will not be sufficient to detect or rule out the myocarditis safety signal that has been noted in older age groups. Ongoing monitoring of the safety and effectiveness in this age group will be essential once the vaccine rolls out into the US community. Australia is fortunate in that we can observe the real world safety data from the use of the Pfizer vaccine in the US to inform any decision we make.