May 3, 2022

In the United States, some parents — and more than a few physicians — are still panicking about unvaccinated children.

Last week, Politico reported that the US Food and Drug Administration might wait until this summer to consider authorising a vaccine for children under five years old. Only a few days earlier, a judge had struck down the nationwide mask mandate on airplanes, prompting angry reactions from some who claimed that the ruling would result in dead children. Some parents have loudly proclaimed that they will continue to shield their kids from social interactions until a vaccine is available. And in New York City, children aged between two and four are still required to mask in schools because they are too young to be vaccinated.

As Covid restrictions and mandates have been dropped across the America and the Western world, unvaccinated kids have become a rallying cause for Americans unable or unwilling to leave the pandemic behind. But the truth is that children under five don’t need to wear masks and don’t need to have their lives put on hold pending vaccination. Hysteria about the risk to them is not just unhelpful but harmful. It deprives them of a normal childhood without any countervailing justification.

A decision on vaccines for young children is probably a few months away, given that U.S. public health authorities want to consider the Pfizer and Moderna vaccine data together. While some parents are understandably angry and frustrated with delay, the FDA is right to be cautious here. Young children are at low risk from the virus and the benefits of vaccinating them are uncertain. Even if the vaccines are approved, it is not clear that they will make a big enough difference to justify placing restrictions on children in the interim.

First, consider that the FDA has not tasked the vaccine makers with proving that their vaccine lowers rates of hospitalisation in kids. Nor do they have to show that the vaccines reduce MIS-C (an inflammatory condition that may arise after infection) or even rates of Covid infection. Rather, the FDA has asked Pfizer and Moderna to prove that their vaccines, at the dose given to kids, generate levels of antibodies that are comparable (or “non-inferior”) to levels of antibodies generated among older, fully vaccinated people. This is a low benchmark, and means that, in practice, the trials being run to clear it are very small. Indeed, they may be too small to detect reliable signals for the most important benefit — reduction in severe Covid — and for harms.

Yet so far, Pfizer has failed to clear even this very low bar. Two doses of three micrograms of the Pfizer vaccine (1/10th the adult dose) fell short in December of 2020, to the disappointment of many. The FDA allowed the company to take another shot at it, literally, by adding a third dose. In late January of this year, there was buzz that the FDA would take the unprecedented step of authorising the vaccine despite the failed trial because it looked like it might reduce infections, but just a week later, Pfizer announced they would wait for the results of the 3rd dose before seeking approval. The flip-flop generated national news and outrage from some parents and doctors.

Then, on March 23, 2022, Moderna announced that its children’s vaccine — two doses of 25 micrograms, or 1/4 the adult dose — did generate sufficient antibody levels, again raising hopes that FDA approval would be forthcoming. But only limited results have been released so far. We don’t know the full spectrum of adverse effects, nor the impact on the outcomes we really care about: cases, severe disease, hospitalisations, MISC-C, and deaths. These outcomes are especially important for conducting a cost-benefit analysis for Moderna, which has clearly been linked to higher rates of myocarditis in young men than has the Pfizer vaccine.

As the clinical trials have dragged on, moreover, the landscape of kids and Covid has changed. Children have always been at relatively low risk, but newer variants appear to be even less risky for them. A recent preprint from the UK suggests that children infected with Omicron were less likely to be hospitalised with severe disease than children infected with the alpha or delta variants. We have also learned that MIS-C is less common often with the newer variants. Delta was less likely to trigger the condition than alpha, and CDC data suggests that omicron was less likely to trigger it than delta.

More generally, it makes no sense to be overly cautious about low-risk children at a time when the United States is dropping most restrictions for adults. The risk to an unvaccinated healthy child under five is often lower than the risk to their vaccinated or even boosted parent. Natural immunity is also powerful and prevalent. It protects strongly against reinfection and even hospitalisation after reinfection. Not that the data here is from adults — naturally immune children are so rarely hospitalised that it is difficult to conduct studies on them.

Most kids have already had Covid, even if they and their parents don’t know it. Prior to the omicron wave, up to half of American children had been infected, and the virologist Trevor Bedford estimates that omicron might have since infected 40% of Americans. Although there is surely some overlap between the two numbers, most kids have probably already had Covid at least once, and it would be difficult for a vaccine to offer them any significant further protection. Finally, we have learned that vaccination has rapidly waning protection against symptomatic infection. Some studies report that vaccine effectiveness in those aged 5-11 for symptomatic Covid is less than 20%.

If you put all this together, the story becomes clear. The vaccine trials have been inconclusive. Most children have had Covid already, and the ability for a vaccine to further improve their health is limited. Finally, they are at extremely low risk to begin with. Parents may encourage their offspring to get vaccinated if and when vaccines become available, but they should not be consumed with fear pending FDA approval. Nor should they prevent their children from living a normal life.