The second dose of the new crown vaccine can be administered even if it is more than 28 days old. In general, the interval between the first and second doses of inactivated New Coronavirus vaccine should be within 8 weeks, so even if the interval exceeds 28 days, it usually does not affect the second dose of the vaccine as long as it does not exceed 56 days. 1. Inactivated New Coronavirus vaccine (Vero cells): Vaccination should be given in two doses, and the interval between the two doses should be more than 3 weeks. The second vaccination should be completed as early as possible within 8 weeks. Therefore, if the vaccine is administered in 2 doses, the vaccination needs to be completed as early as possible within 56 days after 28 days; 2. Recombinant new coronavirus vaccine (adenovirus vector type 5): one dose is administered, so if the population has received one dose, the second dose is not required; 3. Recombinant new coronavirus vaccine (CHO cells): three doses are required, and if this is the dose, the vaccination time for the two adjacent doses need to be at least 4 weeks, i.e. 28 days. The second dose should be completed within 8 weeks of the first dose, and the third dose should be completed within 6 months of the first dose if possible. Therefore, the second dose can be given more than 28 days for both the 2-dose and the 3-dose vaccines, so if you miss the vaccination time, you should make up the corresponding dose as soon as possible within the specified time in order to have a better effect on antibody production after vaccination.