The first two doses of NeoCrown vaccine with Vero and the third with cho are in principle possible and belong to the sequential booster vaccination program. Vero neo-crown vaccine refers to inactivated neo-crown vaccine and cho neo-crown vaccine refers to recombinant protein subunit vaccine. It is generally accepted that no mixing of vaccines from different sources is permitted in the basic immunization program, i.e., the full course of inactivated NeoCrown vaccine or other types of the same vaccine must be given to complete the full course of vaccination. When booster shots are given, the use of a sequential booster vaccination program can stimulate the body to produce a better booster effect, and the use of a sequential booster vaccination program has been implemented in some areas of China. Therefore, it is considered possible to administer the recombinant protein subunit vaccine in the third dose after the first two doses of inactivated New Crown vaccine. For details, consult your doctor before vaccination.