I got the second dose of the Moderna vaccine 28 days after the first. The first time, I had no side effects. The second time, I started to feel fatigued and had a sore throat a few hours after the shot. The sore throat disappeared within 30 minutes but the fatigue continued into the next day, when I developed a temperature of 100.5. In addition, I had subliminal nausea and reduced appetite. This sounds worse than it was. The symptoms did not interfere when I had to shovel snow for 3 hours (and I felt better doing that activity than sitting around). All ill effects were gone the next day.
My wife just received the first dose of the Pfizer vaccine and, a day later, her only "complaint" (and that's much too strong a word) is that her arm has a very minor soreness at the injection site. We fully expect that she will have some side effects when she gets the second dose, so we will be prepared.
Some advice from an RN and MD: If you need to take medication to reduce your discomfort, take Tylenol ONLY. DO NOT USE Advil or aspirin. (This applies to generics, naturally.) This advice applies specifically to the COVID vaccine and is not a recommendation for any other use. For the record, I never was ill enough to feel compelled to take Tylenol.