One has to wonder how much transparency there is in any reporting of child deaths due to the vaccine. Headlines like this are a flash in the pan:

13-Year-Old Dies in Sleep After Receiving Pfizer COVID Vaccine; CDC Investigating

They appear and are quickly forgotten, and we never learn what caused such deaths. There was that case very similar to this one from many months ago. Do they ever report their findings?

My guess: At the heart of Covid there is a cultural war going on. Those that questioned the origin or were vaccine/lose-all-my-freedoms hesitant are a threat to established science culture which loves telling everyone what's good for them and trading off their the science rightness.

When people feel their culture is under attack they close ranks - become reactive, emotional. As it turns out their ranks are large strong ones. So we've now got a situation where doctors, to avoid supplying fuel to those they fear would seek to use the info against their culture, are inclined to under-report adverse effects. It's a normal human reaction. Only trouble is they have abnormal power.

This video contains a pro-bike rider referred for psychiatric treatment when he complained of heart problems.
https://youtu.be/H7inaTiDKaU?t=1