I had adverse cardiovascular issues soon after the vaccine. I've wondered about this, but as far as I can tell the 'covid would have been worse' argument is not definitive. At least with later strains, virus / spike protein may be more localized in the respiratory system than vaccine (at least in cases where the administration inadvertently crosses a vein. I've seen some studies on both sides of this argument, but nothing that was compelling to me. It didn't match my personal experience, that's for sure.

I had my adverse event with the second shot from the vaccine. I was scared to get the booster, eventually got COVID over a year (18 months?) since the original vaccine, so presumably it was offering no protection at that time. I got sicker with COVID. It was unpleasant, but it was 'like the flu, but different.' Very much a respiratory ailment.

My heart was not seemingly affected at all. I had an increase of 5-10 beats per minute for a day or too, which I also got with the flu. Following the vaccine I had a spike in resting hard rate north of 100 BPM almost all the time for months. I'm young, healthy, exercise a lot, etc. The period after my vaccine felt like I was in a bad way and it took a long time to recover.

I was so confident in the vaccines that I initially assumed I was developing a severe anxiety disorder. It was not good.

I can't conclude anything definitive from my anecdotal experience, but I'm not going to touch any mRNA vaccine until these cases are studied and understood.