The interval between two adjacent doses of vaccine needs to be determined by the type of vaccine, whether for students or adults. The interval between two doses of the new crown vaccine is generally 21 days, mainly to allow for full absorption and metabolism of the vaccine and to provide immunity. Hepatitis B vaccine generally requires three doses, with the first dose given within 24 hours of birth in accordance with the “0-1-6” protocol, followed by the remaining two doses at one month and six months of age, respectively. Other vaccines are generally administered according to the age and characteristics of the vaccine to ensure effectiveness. In addition to the characteristics of the vaccine itself that can affect the interval between vaccinations, if a patient has various acute or chronic diseases, such as convulsions, epilepsy, kidney disease, liver disease, respiratory disease, cardiovascular disease, etc., or is in the process of fever caused by various factors during the vaccination period, vaccination should usually be postponed or cannot be given. The main consideration is the medical condition, and therapeutic drugs may also have contraindications with vaccine components. In addition, if a patient unintentionally receives another type of vaccine during the interval between vaccinations, in order to avoid chemical reactions between components that may cause unnecessary harm, it is recommended that the patient truthfully explain the situation to the doctor, who will determine whether the vaccination needs to be postponed, and seek medical attention promptly if there are uncomfortable symptoms.