I've had my booster recently. After all the horror stories from friends and colleagues about how ill they were afterwards, I booked it for a time when I could rest for a couple of days if needed.
Nothing at all. Not even a sore arm. The same for the others, just once the arm was too sore to lay on at night but nothing worse than that.
Colleagues have had up to a week off they've been so ill! Am I just lucky or is there a reason I haven't felt ill? I did have Covid last December, before any vaccinations.