Vaccination of under 12-year-olds: a complex decision

While several countries have started to vaccinate children under the age of 12 against COVID-19, a review by the University of Fribourg and the Murdoch Children's Research Institute (MCRI) in Melbourne makes the point that evaluating the risk-benefit ratio of COVID-19 vaccination in children is more complex than in adults, the reason being that COVID-19 is often asymptomatic or benign in this age group and that there is less safety data available.

This review by an international panel of experts in paediatric vaccination does not argue either for or against vaccination, but highlights some of its sensitive aspects and underlines the complexities involved in making decisions about vaccinating children under 12 years of age. «Whether all children should be vaccinated against COVID-19 remains an open question from a scientific point of view,» says Nigel Curtis, Professor at MCRI and the University of Melbourne. The risk-benefit ratio is less straightforward in children than in adults, particularly because the effects of vaccination and the disease are as yet less well known in this age group.

The case for vaccination
«Apart from protecting the few children who become severely ill with COVID-19, the main argument brought forward to justify vaccinating healthy children is to protect them from the effects of long COVID and, in rare cases, multisystem inflammatory syndrome,» says Dr Petra Zimmermann of the University of Fribourg. «Vaccinating children could also help avoid quarantine, lockdowns, constant testing and school closures.»

And the case for caution
The review also suggests that as long as COVID-19 remains a mild disease in children, it may not be necessary to vaccinate those under 12. This would not only avoid the rare side effects of the vaccines, but would also help improve the supply of vaccines worldwide. «The pandemic has disrupted routine childhood immunisation schedules in many places», says Dr Petra Zimmermann. «Implementing a universal programme of COVID-19 immunisation for this age group risks exacerbating delays in some countries, due to lack of resources and personnel. That said, one could consider combining routine immunisation with vaccination against COVID-19 in order to reduce this risk.»

Lack of insight
According to the study’s authors, there is still a lack of solid data to confirm that the benefits of vaccinating children under 12 outweigh the potential risks. A phase 2 trial of 2,500 children aged 5-12 suggests that mRNA vaccines are safe, well tolerated and produce a strong immune response. Results from the same trial in children under 5 are expected by the end of the year.
For its part, the US Food and Drug Administration (FDA) has recently recommended the Pfizer vaccines for children aged 5-11. In Switzerland, the authorities are waiting for more safety data before giving the green light.

A differentiated vaccination policy
The authors of the study consider that the risk-benefit ratio must be constantly reassessed, particularly if a new variant emerges to which children are more susceptible. In disadvantaged countries, the threshold for vaccinating children under 12 years of age could be crossed more quickly, since COVID-19 is often more severe in children there due to the greater frequency of underlying diseases. A single or reduced dose of vaccine could be an option, in particular to reduce the albeit low risk of myocarditis experienced after the second dose of a messenger RNA vaccine.

Publication: Petra Zimmermann, Laure F Pittet, Adam Finn, Andrew J Pollard and Nigel Curtis. ‘Should children be vaccinated against COVID-19?’ Archives of Disease in Childhood. DOI: 10.1136/archdischild-2021-323040