Young kids catching COVID: how much to worry?

Low confidence, slapdash job. Just putting this up in case other people want to compare notes.

Now that all the adults in my family have been (at least partially) vaccinated, my kids will soon be the most COVID-vulnerable members of my family. Therefore it is newly decision-relevant to get a good sense for exactly how worried I should be about them catching COVID-19. This is April 2021, Boston area, two kids under age 7.

Target audience: Frequent readers. Everyone else, go away. This is written for people who treat 1-in-10,000 risks as dramatically, wildly, viscerally scarier than 1-in-100,000 risks, people who understand that “zero risk” is a thing that does not exist in our universe, people who understand that life is full of tradeoffs, including between mental health and physical health, etc. etc. etc.

1. Death from COVID-19:

According to this paper written in August 2020 Fig. 2, the IFR is ~3/​100,000 for age 0-4, <1/​100,000 for age 5-9. I personally can probably adjust that downward from the known lack of risk factors. So that’s very low—not worth sacrificing significant quality-of-life over. (That’s like a month or two out of a reasonable fatality risk budget, I figure—even less since we’re not making decisions that swing the risk of COVID-19 infection all the way from 0% to 100%.)

2. MIS-C:

“Multisystem Inflammatory Syndrome in Children” is a frightening syndrome that can produce severe problems including heart problems, neurological symptoms, strokes, and so on. CDC says (via NYT) that they know of 3185 cases (of which 1% were fatal, but death is already included in the previous section) as of this writing. I’ll ignore the possibility that there are more MIS-C cases that the CDC doesn’t know about—this is a pretty serious and well-publicized condition, I presume that most kids with MIS-C are being hospitalized and diagnosed. CDC says most cases of MIS-C were ages 1-14, which is I guess a population of 60M in the USA. I dunno how many kids have been infected with COVID total, but if it’s similar to the prevailing rate (figure 28% including undetected cases), then we’re around 2-in-10,000 risk of getting MIS-C, conditional on catching COVID. (The number of detected cases in kids is disproportionately low compared to the rest of the population, I think, but I’ve always just been figuring that they’re less likely to be symptomatic than adults and therefore have an unusually low detection rate.)

Mayo clinic says “In rare cases, MIS-C could result in permanent damage or even death.”, which (accidentally) implies that almost all the time, kids who get MIS-C fully recover without permanent damage. That’s not a great source, but whatever. Also, this says that 77 MIS-C cases at a particular hospital were “fully recovered”.

So I figure, conditional on a kid catching COVID, there’s a 2-in-10,000 risk of getting MIS-C, going through a somewhat terrifying ordeal, but eventually fully recovering. And, there’s a, I dunno, 1-in-100,000 risk of permanent problems. Again, combine that with the fact that I’m not making decisions that swing the risk of COVID-19 infection all the way from 0% to 100%, and I find this a pretty much acceptable price in cases where I’m spending it on real benefits in my kids’ mental health and quality-of-life. Unless my numbers are wrong of course. So I’m pretty much ignoring MIS-C too. The next two categories seem much worse than that.

3. Long COVID:

Children with long covid” (New Scientist, Feb 2021) says “Evidence from the first study of long covid in children suggests that more than half of children aged between 6 and 16 years old who contract the virus have at least one symptom lasting more than 120 days, with 42.6 per cent impaired by these symptoms during daily activities.” What??? 43%? No way. That’s way too high. This article calls it rare. 43% is not rare.

The 43% statistic comes from Preliminary Evidence on Long COVID in children. It seems like a helpful article but I don’t know what to make of the selection bias. Where exactly did they get these kids? “This cross-sectional study included all children ≤18 year-old diagnosed with microbiologically-confirmed COVID-19 in Fondazione Policlinico Universitario A. Gemelli IRCCS (Rome, Italy).” That should disproportionately sample sick kids, and especially severely sick kids, right? So I’m going to ignore that.

The New Scientist article also says “The UK Office for National Statistics’s latest report estimates that 12.9 per cent of UK children aged 2 to 11, and 14.5 per cent of children aged 12 to 16, still have symptoms five weeks after their first infection.” That’s this link. I’m guessing that the population here is “initially-symptomatic kids” as opposed to “all infected kids”. So divide by 2 or 3? And not all of those 12.9% are catastrophic. Some may be kids who are easily-fatigued for 5 weeks then recover, which kinda sucks but isn’t that big a deal. I dunno, figure, conditional on a kid catching COVID-19, 2% chance that it’s, like, a really really long and miserable slog that everyone will deeply regret. The rest of the time it’s at worst in the ballpark of adding up 1 unusually severe flu + 1 broken leg—lots of pain, hassle, doctors visits, medical bills, missed activities, and so on, but not worse than that. Life goes on.

4. Long-term complications:

Maybe you catch COVID as a kid and then there’s a 1% higher risk of heart disease decades later. Or something else. How would we even know?

My general impression is that kids’ bodies are generally good at recovering and rebuilding themselves over time. But that’s not really based on anything. An example in the opposite direction is polio: I guess polio kills nerve cells in a way that’s unrepairable, and which gradually gets worse and worse over decades after apparent recovery? Is the nervous system unusually hard to repair?? Because, um, COVID often impacts the nervous system too, right?! Yeesh.

I have no idea, I’m out of my depth here.

I guess I’ll say 1% chance of a big-deal long-term latent problem, conditional on catching COVID-19. That’s not really based on anything, but I need a number because I have to make decisions and weigh tradeoffs. Happy for any input here.


So, conditional on a kid catching COVID, I guess I’m currently thinking that I should mainly be weighing a ~2% chance of a miserable months-long ordeal until they recover, plus (overlapping) ~1% chance of a big-deal long-term latent problem that will show up later in life.

OK, I guess when I multiply everything out right now…

  • Any masked outdoor activity

    • Risk rounds to zero, do it without thinking twice.

  • Fully-vaccinated adults (6+ weeks past 1st dose) spending time indoors unmasked with my kids

    • If the adults have not recently been spending extensive (or unmasked) time indoors with unvaccinated people, then no problem, don’t even think twice about it. If they have, then try to avoid it, but maybe it’s OK from time to time if there’s sufficient social benefit.

  • Somewhat-vaccinated adults (2-6 weeks past 1st dose) spending time indoors unmasked with my kids

    • If necessary. Depends on what the adult has been up to and how much social benefit we’re getting out of it.

  • Kids go to school (masked)

    • We’re already doing that. Our local school is pretty good about ventilation and masking, and has mandatory universal weekly PCR testing. Any remaining risk is more than compensated by the very large benefits for both kids & parents.

  • Kids spending time inside with other kids

    • I guess on rare occasions if there’s a sufficient social benefit. But definitely try to keep such activities outside, until community spread goes down from its current high levels. Oh, I guess there should be an exception for school classmates, since they’re already spending time together inside masked, every day at school. But go for masks and open windows.

  • Kids tag along shopping indoors, masked

    • Check the microcovid calculator, but probably not if it’s avoidable, at least not until community spread goes down from its current high levels.