I've only had a reaction to a vaccine once and that's when I went from having the Pfizer covid vaccination to getting the Modema vaccination as the 6 month booster shot. I had a fever and extreme chills where my mouth was chattering so much that I wore a mouth guard because I was afraid of cracking my teeth. It lasted for about 90 minutes, then I was totally ok. The pharmacist did tell me that he also had a reaction to that particular vaccination because it was stronger than the previous ones.

I now stick to Pfizer covid vaccinations.