There is usually no obvious difference between two or three shots of New Crown for the elderly, and the choice can be made according to one’s own needs. Since the protection mechanism of the New Crown vaccine will be different between two and three injections due to the different technologies used, both of them have been approved by the State Drug Administration after a large number of clinical trials, and both have their own advantages, and both of them can play a protective role, and it is not possible to judge which one is more effective by the number of injections. The two-dose XKV is an inactivated vaccine whose immune components are similar to those of the virus, which has the advantages of a strong immune response and good safety. The three-dose New Crown vaccine is a recombinant protein vaccine, which is immunized by genetically engineered effective antigenic components expressed in cells in vitro, with no involvement of the virus in the whole process, making it safer and with a relatively low probability of adverse reactions. To be on the safe side, seniors can consult with a medical professional if they choose to receive two or three doses of the new crown.