But I do not believe that this is valid at all, being that this is the very first mRNA vaccine.

>By looking at other vaccines historically and seeing that side effects tend to happen in the first few weeks.

I feel like what you are saying is basically like someone asking "How do we know that self driving cars will be safe on the road" and you responding with, "well obviously by looking at the history of cars, we have been doing them for a century!"