The third shot of the vaccine may refer to the new crown vaccine, the menstrual period does not come may be after sex to lead to pregnancy, may also be endocrine disorders, and the vaccine has little to do with. 1. Pregnancy: If your period is delayed for more than seven days, use an early pregnancy test strip to see if you have a double bar, and to be more accurate, it’s best to take a blood test for HCG to confirm whether you’re pregnant, or not, and you won’t be able to get your period after you’re pregnant. 2. Endocrine disorders: due to nervousness after vaccination, poor diet, excessive weight loss, diet pills, staying up late and other reasons, may lead to endocrine disorders caused by menstruation staggering. In addition, there are many other factors that can cause menstruation, it is recommended to go to the hospital in time for examination, to clarify the cause of the disease, and then follow the doctor’s instructions to deal with the treatment.