Covid-19 vaccination in children

The recent decision by the US Food and Drug Administration (FDA) to extend an emergency use authorization (EUA) for the Pfizer-BioNTech covid-19 vaccine for children from 12 to 15 years has sparked dissent from some stakeholders. While we acknowledge the concerns of other commentators, we’d argue that this was the correct decision, both for children and for the societies of which they are a part. Covid-19 poses a risk to children, and protecting them should be our primary focus. Vaccination is the best way to achieve this.

An estimated 191 641 children in the US have been hospitalised with covid-19 at a frequency of 1-3% of cases over a 13 month period, although recent data suggest that this may be an overestimate, as approximately half may reflect incidental covid-19 diagnoses in the hospital. Provisional reports from the US Centers for Disease Control and Prevention (CDC) note that from the start of the pandemic to the start of June 2021 there have been 441 covid-19 pediatric deaths in a sampling of 476 243 deaths for which age was available. This is therefore an undercount as an estimated 584 284 deaths were reported to the CDC up to June 2021 citing covid-19 on the death certificate and this is more consistent with excess mortality data. For comparison: varicella caused  approximately 11 000 hospitalizations and 100-150 deaths per year in the pre-vaccine era. 

Furthermore, in the US alone, there have been 4018 cases of Multisystem Inflammatory Syndrome in Children (MIS-C) up to the start of June 2021, with 35 deaths. Children also risk post-acute sequelae of SARS-CoV-2 after infection (PASC), although the true significance of this is only likely to become apparent in the coming months. Given strong evidence that vaccination can prevent even asymptomatic infection, protection should be extended to the pediatric cohort.

Transmission from children occurs primarily within households rather than in schools. It is estimated that around 40 000 parents have been lost to covid-19 in the US, and children may have acted as the vector in some cases—although we do note that in most cases of intra-household transmission, adults infect children rather than the reverse. Relative to adults, children frequently present with milder symptoms, and a higher proportion are asymptomatic despite high viral load, thus increasing the likelihood of spreading covid-19 as other hosts lose their potential for infectiousness via vaccination. Prevention requires substantial non-pharmaceutical interventions within schools, which may not be universally implementable in resource-poor districts and are an ostensible barrier to normalcy in the classroom, which can have adverse educational and mental health impacts. Vaccination therefore represents a definitive path to normalcy for children.

Concerns have been raised about the regulatory pathway by which these vaccines arrive. The principal differences between emergency use authorization (EUA) and biologics license application (BLA) pathways are a minimum of two months of follow-up for the former (via a 60 day period of active reporting including both solicited and unsolicited adverse events), but six months for the latter. Given the public health emergency posed by covid-19, vaccinations in the US have been authorized via an EUA pathway. As the vaccines have already been granted EUA for adults, the extension of the indication to younger patients is not an extension of the declaration of emergency to children; rather, it is representative of the scope of the existing public health crisis, the inherent risk to children, and the ability for children to serve as vectors to the most vulnerable members of society. It is unlikely for any non-live vaccine to produce adverse events beyond two months after vaccination and we are unaware of any examples in which this has occurred. Thus, given the present emergency, a four month delay to access is unlikely to produce any meaningful new safety data, but will ensure preventable harm in children who develop covid-19.  

The limiting variable for sensitivity to capture rare adverse events following immunization (AEFI) is most properly regarded as the sample size rather than the duration of follow up. Historically, phase III trials for vaccines have included as few as 5000 individuals, and even fewer when examining specific subpopulations as is the case here; Moderna’s TeenCoVe study includes 3235 individuals aged 12-17 years and Pfizer’s trial includes 2260 individuals aged 12-15 years. Certainly, it would be unreasonable to expect trials of this size to capture very rare AEFIs. Even if 30 000 individuals receive a vaccine in a clinical trial, events rarer than 1 per 10 000 doses are likely to be missed—hence a reliance on pharmacovigilance for the detection of rare AEFIs. The sensitivity of current surveillance appears robust as recently demonstrated by the cases of thrombosis with thrombocytopenia syndrome (TTS) associated with the Janssen (Ad26.COV2.S) vaccine: an event that was initially noted in fewer than one per million doses. More recently, questions have arisen around the possibility of myocarditis from (in particular) the second dose of the BNT162b2 mRNA vaccine in young males, but these risks remain unconfirmed at this time, and the associated cases reported to date have been predominantly mild. Consequently, the balance of risks and benefits still remains highly favorable even if the finding is found to be causal—though patients should be apprised accordingly.  

We additionally note that vaccination is an essential public health intervention that protects the vaccinee (direct vaccine effects) and the population (indirect vaccine effects). The true value of any vaccination campaign is measured by the public health gains incurred rather than the value to any given individual, which is especially apparent for diseases like chickenpox, rubella, and even measles. Those under the age of 18 make up 23.6% of the US population; while the herd immunity threshold for covid-19 is unknown, it is unlikely that leaving nearly one quarter of the country unvaccinated is conducive to its attainment. Thus, even if one disregards the risks posed by covid-19 to the pediatric population directly, there is still considerable benefit to ensuring their vaccination.

In our view, the current evidence unequivocally supports that the potential benefits far outweigh the potential risks of this choice. We should pursue this opportunity in an equitable manner, rather than minimizing covid-19 and perseverating on unsubstantiated concerns.

Edward Nirenberg is a science communicator and vaccine advocate. He has no conflicts to declare.

Daniel A. Freedman is a pediatric neurologist at Dell Medical School. He has no interests to declare.

Risa Hoshino is a practicing board-certified pediatrician working in public health. She has no interests to declare.

Jonathan Howard is an associate professor of neurology and psychiatry at NYU Langone School of Medicine. He has no interests to declare.

Alastair McAlpine is a pediatric infectious diseases physician at BC Children’s Hospital. He has no interests to declare.

Acknowledgements: We would like to extend our sincerest gratitude to Senior Pharmaceutical Regulatory Affairs Specialist, Andrea Bailey, PhD, for her editorial assistance and consultation for this work.