My brother had a heart attack in December, soon after the rest of my brothers and sisters (and my mother over my objections) got their boosters. He has kept a very low profile, and no one could tell me if he had gotten one as well. I finally got a chance to ask him a couple of weeks ago if he got the booster, and he became really upset and angry, and said it had nothing to do with his heart attack. His wife also has some autoimmune thing where her hands swell up. No one in the family thinks there's anything unusual there. Some people will never wake up.