The interval between the first and second vaccine doses may vary depending on the type of vaccine and there is no absolute maximum interval. A vaccine is a biological product made from a pathogenic microorganism that is used for prophylaxis. Most vaccines require multiple vaccinations to enhance their preventive power, and the time required between vaccinations generally varies depending on the type of vaccine. For example, the interval between the first and second doses of the hepatitis B vaccine is about one month, the interval between the nine-valent HPV vaccines for women is about two months, and the interval between the two doses of the new Crown vaccine is about six weeks. If the vaccine is given for the second time beyond the appropriate time limit it does not mean that it needs to be revaccinated, the patient can still continue to be vaccinated in the same order as the last vaccination, but the patient needs to inform the doctor at the point of vaccination or the epidemic prevention department in advance. Patients are advised to maintain a light diet after vaccination, avoiding spicy and stimulating food that may affect the normal functioning of the vaccine, and try to complete the next vaccination within the time limit, and ask the doctor in advance about dietary and medication contraindications during the vaccination.