Safety is not a binary condition. The vaccines have a good safety profile as confirmed through large-scale clinical trials, and have met stringent FDA criteria. However the risk isn't zero. The CDC has acknowledged a small risk of myocarditis for the mRNA vaccines.

https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/my...

This isn't generally a reason to avoid vaccination for most of the population, however the risk / benefit ratio may be different for some sub-populations. In particular there has been a higher than expected rate of adverse cardiac events for adolescent males.

https://www.medrxiv.org/content/10.1101/2021.08.30.21262866v...

So particularly for those adolescents who have already recovered from infection and have no other risk factors we should have a scientific discussion about whether vaccination makes sense from an evidence-based medicine perspective. Unfortunately the issue has been so politicized that any suggestion of caution often gets misinterpreted as being anti-vaccination.