The third vaccine, usually referred to as the New Crown vaccine and the 9-valent HPV vaccine, does not affect menstruation. The vaccine stimulates the body’s immune system to produce antibodies and does not affect the endocrine system, so it does not cause menstrual changes. The HPV vaccine uses inactivated human papillomavirus as an antigen to induce the body to develop humoral immunity to produce an effective amount of antibodies to fight against human papillomavirus infection, which is a means of activating the body’s active immunity. It also does not affect the ovarian endocrine system or cause menstrual changes. Women’s menstrual disorders after the third vaccination with the New Crown vaccine or the 9-valent HPV vaccine are actually not a direct effect of the vaccine, but may be related to the recent stressful moods, late nights, anxiety, tiredness, etc., which affects the normal endocrine regulation leading to abnormal secretion of ovarian hormone levels, thus causing changes in menstruation. For patients whose menstruation is affected by the third vaccination, it is recommended that they go to the hospital in time for examination to clarify the cause of the disease and then follow the doctor’s instructions for treatment.