EDIT: more respectful title.
So my FIL isn't really all that terrible politically-speaking, and was even one of the human trial volunteers for the original COVID vaccines (can't remember which).
However, he did spend much of the larger pandemic years obsessively watching youtube videos by a handful of people claiming to be doctors who would do weekly news updates on stuff like vaccination progress, covid mutations, just general "pandemic content" which also seems to have covered side effects and concerns with the vaccines.
That's to be said, that now if current COVID vaccines are mentioned in any way he'll mention stuff like "heart problems" and "lung damage" and "rolled out too quickly" etc. which comes off (to me) as anti-vax paranoia, but I also don't really know how to properly research this shit myself because I'm not an immunologist!
Of course there's the usual capitalistic bullshit with COVID vaccines as there are with other vaccine programs, such as how the imperial monopolized the vaccine efforts to exploit it for $$$ in the global south (and in turn, created an endless pandemic hellhole). However, in terms of its safety and effectiveness I can't say I buy much of the claims because we've seen how even this botched vaccine rollout correlated with massively reduced hospital admissions and long term COVID effects.
EDIT: I've added a few links I've found while researching this myself in the comments. I hope some of this info is useful to people other than myself, and hopefully I've understood some of it properly. I didn't want to ask a question like this and not do any work on it myself!
The risk of myocarditis is present every time you get covid, because covid is a vascular disease and can directly attack your heart.
There is also a risk of side effects every time your immune system is activated, which vaccines purposely do. A real virus will always cause worse harm, because it's an active infection attacking your body, and not just a vaccine that is mostly inert and designed to trick your body into reacting.
https://www.wsws.org/en/articles/2024/03/06/sfvw-m06.html
It should also be noted that during the vaccine rollout we never had covid fully under control, and it was very much present in a lot of communities, especially younger folks where most of the side effects were noticed, since so many people assumed young people weren't effected by covid. I'm not sure if any safety review took this into account, but the chance that people got covid before the vaccine took effect (like if they went back to normal immediatly and didn't wait two weeks) was not insignificant.