OMG Sick Reaction to Booster

While it is possible your GI symptoms are due to the vaccination, 2 hours is awfully fast. Looking at the literature, around 3% of vaccine recipients report diarrhea. The other symptoms you report are common. If the diarrhea doesn’t clear within a day or so, you should have stool cultures done to eliminate other causes. By any chance have you been on antibiotics within the past 7-10 days?