This is the expert consensus based on everything they know about how immunity and mRNA works.
It's kind of hard to give you one single source, simply because it's hard to demonstrate the absence of something. What usually happens instead is that somebody with specific concerns raises them and explains the plausible mechanism they see as problematic, then it's either debunked immediately as BS or if the theory has legs, it's supported by other scientists and put the test.
None of that has happened with mRNA vaccines. This is a great read about the Pfizer one : https://berthub.eu/articles/posts/reverse-engineering-source...
I mean, you can't technically rule out somebody coming up with a revolutionary theory that changes our understanding of immunity like Einstein did for physics, but there is no sign of that, no theoretical basis for trouble, and the vaccine is saving lives in the meantime
>Also, what about people who have antibodies from prior infection with covid?
Research is moving fast on this, but AFAIK the consensus is that prior symptomatic infection gives longer lasting but also less broad (against different variants) immunity compared to an mRNA vaccine.
The best protection seems to be in people with prior infection + 1 shot of mRNA vaccine (of course, that does not imply one should try to get infected then vaccinated, because the risk of damage from that first infection vastly outweighs the benefit of a slightly better immunity if you pulled through unscathed, then got vaccinated)