Vaccines do not cause delayed menstruation, while delayed menstruation after vaccination may be related to other reasons. Vaccines are mainly made of attenuated or inactivated pathogenic microorganisms, and their main purpose is to react with the immune system in the body to generate antibodies and enhance the body’s immunity against certain infectious diseases. Common side effects include fever, dizziness, fatigue, joint tenderness, localized redness and swelling at the injection site and other systemic and localized reactions at the direct injection site, and do not cause delayed menstruation. Menstruation is affected by hormones such as estrogen, progesterone, and androgens, and these hormones are greatly influenced by factors such as emotions, lifestyle habits, and physical health, etc. Problems with one or more of these hormones can cause delayed menstruation. In addition, pregnancy can also delay menstruation. It is recommended to stay in the observation room for 30 minutes after the vaccination, during which time you can seek medical attention if you feel unwell. Don’t touch water on the vaccinated area for 2 days after returning home, take proper rest, choose foods rich in quality nutrition such as lean meat and milk in your diet, and avoid spicy and stimulating foods such as alcohol and chili. If menstruation does not come for a long time, it is recommended to go to the hospital to find out the cause and get timely treatment if necessary.