I'm type O....Wife and I have had both Pfizer shots (got shot #2 a week ago). Shot #1, no problem, but oddly enough, that arm is still a little bit sore! Shot #2, I woke up the next morning with a headache, took 2 Tylenol, and that seemed to take care of that. Felt a little off that morning, but by afternoon felt pretty normal. Got the second shot in my other arm, and that one feels fine. Wife has been fine after both shots.