Exactly this. Saturday night before last, we went to karaoke for the first time since October. There were maybe 30 of us there. Several of my friends had gotten the vax. We sang, laughed, hugged, and remembered the normal days. Sunday morning I woke up with the worst headache ever (I don't drink, so not a hangover). I felt just bad all day. Monday I didn't get out of bed, headache and just no energy. Hubs picked up some Ivermectin for me at Tractor Supply, and I was back to almost normal on Tuesday and 100% by Wednesday. I hope that is it, and that it doesn't reoccur, but I'm definitely leery of spending more time with my vaxxed friends until we know more.