I normally have very regular, very light flow periods that last 2 days max. Before my first AZ vaccine in june I hadn't a period in 5 months. At 48 at time I assumed it was menopause. A few days after the vaccine I got the most excruciatingly painful insane level of heavy period that lasted almost 2 weeks. Since my periods are not regular and heavier than normal and last 3 days not 2. Which doesn't sound much but it is 50% longer!