Hi ! I hope you get some input from the community here before you get your booster. We don't have any other forums or threads specifically about booster reactions yet, but I have been paying attention to comments in our Facebook community. Few have gotten the booster at this point. Of those who have, some have mentioned more arm soreness than after the previous shots, but that is the worst I have heard so far. It might still be too early to know whether the boosters result in flares. I hope yours goes well and that you have no side effects. If you wouldn't mind posting an update afterward, that might be helpful to others Thinking of you! - Lori (Team Member)