I had my booster at the beginning of December and my period arrived right in the 2 weeks after. We started TTC for a second baby right afterwards. This month my period was due on Tuesday and so far no sign. It's usually like clockwork so being four days late is very strange. I did a pregnancy test last night and it was negative (clear blue early detection). Could the delay be due to the booster? Any one had their periods affected? Mine were really heavy after the 2nd vaccine, but still on time. I don't want to get my hopes up.