After my second Moderna shot I was completely mumped for about 36 hours. Constant fever near 103, chills/sweats, bad headache, even threw up. Then all of a sudden I felt completely fine. It seems pretty random how it hits people. I’m 35 ,in relatively good shape, and was wrecked, but a decent amount of my coworkers who are pretty old (and let’s just say not in the greatest of shape) had zero issues outside of a sore arm.