What are the possible causes of a woman's absence of menstruation?

Possible causes of absence of menstruation in women can include factors such as stress, illness, fatigue, changes in schedule, or even receiving a COVID-19 vaccine. It is not uncommon for menstrual cycles to become irregular or stop altogether after receiving certain vaccines, but typically this issue resolves on its own. In some cases, medication may be prescribed to help regulate the menstrual cycle if deemed necessary after a medical evaluation.