My understanding is that Serious Adverse Events are not necessarily reactions that can easily be attributed to the vaccine (unlike a headache occurring soon aft

My understanding is that Serious Adverse Events are not necessarily reactions that can easily be attributed to the vaccine (unlike a headache occurring soon after the vaccination), so we have to check whether these results are statistically significant and/or whether any patterns can be found in terms of what these events actually are. I don't think 0.4% vs. 0.1% with n=1127 is significant, and the study mentions no patterns were observed. We still have systems like VAERS to ensure side-effects that are too rare to be caught by a study of this size still get caught.