Hypothetical question:

Having heard vaccinolgists explain how often side effects (including serious side effects such as seizure disorders, etc) are not caused by the vaccine itself but are because the person had a genetic disposition to such a reaction if they had been infected by the wild virus. 

Would this be true also with mRNA vaccines since they do not contain any part of the virus or is there a possibility that none of these potential side effects could occur? Has this been explored or discussed?