It is rare for a vaccination to cause delayed menstruation. After vaccination, a series of adverse reactions such as dizziness, pain at the injection site, nausea, diarrhea, fever, etc. usually occur, and if the adverse reactions are serious, attention should be paid to timely medical treatment. If menstruation is delayed after vaccination, it may be caused by excessive psychological stress, anxiety and nervousness about vaccination, or endocrine or pituitary dysfunction due to poor diet, cold, or late night, which may lead to delayed menstruation. In addition, pregnancy and some diseases may also lead to delayed menstruation. It is common in the following cases: 1. General factors: Some women may worry about the adverse reactions of vaccines and have high psychological stress after vaccination, which then affects the endocrine secretion of the organism and leads to the postponement of menstruation. In addition, the influence of factors such as poor diet, cold, late night, overwork, etc., which make the hormone level in the body imbalance, may also lead to the delay of menstruation. It is recommended that women should not worry too much and pay attention to self-stress regulation, such as diverting their attention through moderate outdoor exercise, listening to music and reading books, etc., and if necessary, seek medical treatment. 2. Pregnancy factor: women will have temporary menopause during pregnancy. If a woman who is married or has a sexual life has delayed menstruation after vaccination without knowing she is pregnant, she may mistake it for the effect of the vaccine. The influence of drugs on hormone levels in the body may lead to delayed menstruation, which may also be mistaken for the influence of vaccines. 4. Disease factors: While vaccination is in progress, women with related diseases such as cervicitis, uterine fibroids, polycystic ovary syndrome, hepatitis, tuberculosis, anemia, abnormal thyroid function, obesity, etc., may also affect endocrine function and lead to delayed menstruation, which may make women mistakenly believe that it is the effect of vaccines. In addition, surgical treatment of uterine cavity diseases may cause adhesions that prevent menstrual blood from being discharged, which may also lead to delayed menstruation. It is recommended that women who have delayed menstruation should visit a hospital in time and undergo relevant examinations, such as reproductive endocrine hormone measurement and ultrasound examination, to clarify whether there are endocrine disorders and organic diseases, and take appropriate treatment under the guidance of a doctor. In daily life, you should develop good eating and living habits, avoid staying up late, pay attention to adjusting your emotions, and exercise appropriately to help your menstruation return to normal.