Among the 28 million Americans aged five to 11, the CDC counted just 66 Covid fatalities in the year ending in October, less than the number who died from the flu in 2019. And the Covid tally is surely an overcount that includes children who happened to test positive but actually died from other causes. (Two-thirds of them had at least one other underlying condition.) In studies analyzing the hospital records of children classified as Covid cases, researchers found that nearly half of the children showed no symptoms of the disease and were being treated for other problems.

In its risk-benefit analysis of vaccines for young children, the Food and Drug Administration estimates that, under most scenarios, only one death would be averted for every 1 million children vaccinated. That’s probably too optimistic, because the calculation is based on overestimates of past Covid mortality (those overcounted deaths by the CDC) and doesn’t account for the reductions in future mortality due to improved treatments. But even assuming that vaccination did prevent that one Covid death in a million, it would take only a small number of deaths from unforeseen side effects from the shot to result in a net loss of life.

Researchers have already identified several rare but worrisome side effects, including blood clots and myocarditis, which have not been adequately investigated. No one knows what else might turn up. When the FDA’s advisory committee approved the vaccine for young children on the basis of a clinical trial, one of its members, Eric Rubin of the New England Journal of Medicine, acknowledged that the trial was too small and too brief to identify rare and potentially severe side effects.