I want to know about it too. I got the flu vaccine in ~2016 and the next day experienced heartburn like I had never experienced before. I had to lay down the rest of the day. I had and have never experienced heartburn like that since. I probably should’ve had it checked but just toughed it out. I had a suspicion it was the vaccine, but no one I knew in medicine had ever heard of it happening.

I didn’t have any side effects with either SARS2 vaccines except for a sore arm, so who who knows what that was!