It's also not like this is the first vaccine, or even the first mRNA vaccine. So we have analogs and precedents we can use. My understanding is that was heavily used in the clinical trials before roll out -- an understanding from previous vaccines that if someone majority were to go wrong it would go wrong in the first few months, and not 5+ years later.

> So we have analogs and precedents we can use.

You gotta be careful. Biology is not always "linearly interpolable" like that.

> "if someone majority were to go wrong it would go wrong in the first few months, and not 5+ years later".

You REALLY can't say that. There are plenty of medical conditions that will not manifest at all until years later.

> You REALLY can't say that. There are plenty of medical conditions that will not manifest at all until years later.

But is that true for vaccines? We've had a hundred years of precedent.

every molecule has different effects. Change the wrong amino acid residue in insulin and you get something that hyperactivates IGF-1 pathway and causes cancer, which you won't see in the short term. You can't be sure that any given vaccine won't accidentally activate an oncogene, until you do the study, and such a study would necessarily take years, or decades.