Myocarditis signal was known in Feb 2021 but FDA and CDC hid it until they got the vaccine authorized for 12-15 year olds in May 2021. Here is the proof.

https://twitter.com/NassMeryl/status/1660464093185155072?

 

https://anthraxvaccine.blogspot.com/2023/05/myocarditis-signal-was-known-in-feb.html