There is no direct relationship between the third vaccination and delayed menstruation. Delayed menstruation may be due to early pregnancy or certain diseases, and it is recommended to go to the hospital if menstruation is delayed for more than a week. 1. Endocrine: Psychological anxiety, irregular work and rest, or prolonged fatigue can affect the endocrine system and cause delayed menstruation. 2. Early pregnancy: After pregnancy, women will experience symptoms of menopause. 3. Diseases: Polycystic ovary syndrome, pituitary tumor, hyperthyroidism and other diseases can also lead to delayed menstruation, and in severe cases, amenorrhea can also occur. If menstruation is delayed for more than one week after the third vaccination of New Crown Vaccine, it is best to go to the hospital for consultation, to clarify the reasons for delayed menstruation through systematic examination, and at the same time, to regulate the situation under the guidance of professional doctors.