You don't know, you can't know that a particular adverse reaction was   

You don't know, you can't know that a particular adverse reaction was directly caused by the vaccination. You know, like I found a single $100 bill on the sidewalk. The $100 wasn't there because of the sidewalk's existence, nor was it there because of the time of day, the weather or the color of my shoes. The money was there because it was there and nowhere else. My finding it and the bill's existence implies no rule of being other than it was there and nowhere else.

The public health stats kept by public health agencies demonstrate that the vaccination does not prevent infections but it does reduce the severity by 73% reducing the probability that a vaccinated person would be sick enough to require in-patient hospital treatment- like respirators. Y