Generally speaking, the new vaccine will not cause a decrease in menstrual flow. If it is due to physiological factors such as disturbed work and rest, stress, etc., no special treatment is needed. If it is due to polycystic ovary syndrome or hyperthyroidism, medication or surgery is needed to treat the cause. 1. Physiological factors: If there is a disorder of work and rest or excessive mental stress after the vaccination, resulting in endocrine disorders, it will easily lead to low menstrual flow, which generally does not require special treatment, and can be relieved after timely adjustment of work and rest and mental state. 2. Polycystic Ovary Syndrome (PCOS): Common symptoms include menstrual disorders, which are characterized by low menstrual flow. Patients should follow the doctor’s instructions to use short-acting compound oral contraceptives such as compound norethindrone and compound methyl norethindrone tablets, as well as progestational drugs such as dydrogesterone and micronized progesterone. 3. Hyperthyroidism: Typical symptoms include prolonged menstrual cycle and scanty menstrual flow. Patients should follow the doctor’s instructions to use antithyroid drugs such as prothioxythiophene and imidazole formamide, as well as beta-blockers such as propranolol. For patients who are not on long-term medication and have a large thyroid gland, total thyroidectomy should be considered. If the menstrual flow is low for a long period of time, you should go to the hospital to find out the cause of the problem and cooperate with the doctor for active treatment. The use of medication should be under the guidance of a doctor.