If a person has a fever after the 3rd day of vaccination, it depends on the fever type and whether the fever is combined with other diseases of the organs. Usually, a person will have a fever within 3 days after the vaccination, but the temperature will not rise particularly significantly, and a temperature of 37.3-38.5°C is normal. However, if a fever appears on the 3rd day after vaccination, it is not due to the normal reaction of the vaccine, but to the weakness of the body after vaccination, and the fever is caused by the inflammatory infection caused by bacteria, virus, fungus or other pathogenic microorganisms. In this case, it is recommended to go to the hospital for routine blood tests, blood bacterial culture, and C-reactive protein, and apply fever-reducing drugs for treatment according to the specific situation.