I had Moderna. I haven't had a period in 15 years. I was on the 3 month cycle of birth control pills due to migraines during my week off. So I'd do 11 weeks on, 1 week off, and should have had a period during the week off but it just slowly got lighter and lighter until I stopped bleeding at all. Last July I turned 50 and stopped taking the pill so my body could go through menopause. I had hot flashes, etc. until January and figured I was done with it all.
Got my second Moderna in March and less than a week later, I started bleeding again. Every other week for the next two months. The first of May I had a period worse than anything I've ever had. I won't get graphic, but it was worse than postpartum. I contacted my PCP and she gave me synthetic progesterone for 8 days. As soon as those 8 days were up, I started bleeding again and this time it was even worse. I didn't think that was possible. So this time I went to see my PCP and she put me on the largest dose of actual progesterone and I have an appointment with a gynecologist in a month just to make sure it isn't something other than the vaccine. I've read enough anecdotally I am pretty sure it's the vaccine, but I'm taking that progesterone and still spotting (which shouldn't happen). I had emergency surgery in early January and it's really messed up my body, so I think when the vaccine caused an immune response, my body just kind of reacted. I hate this though. Didn't really want to go through all of this again.