The reason why the number of shots for different vaccinations varies is mainly due to the different production methods of different vaccines, the time duration of producing immunity, etc., but ultimately they all achieve immunity against specific infectious diseases, so it is impossible to compare the advantages and disadvantages of the two-dose and three-dose vaccine programs with each other. Common three-dose vaccines include HPV vaccine, hepatitis B vaccine, and diphtheria vaccine; common two-dose vaccines include hand, foot, and mouth vaccine, polio vaccine, and influenza vaccine. Most vaccines cannot achieve effective resistance to viruses with only one injection, so multiple vaccinations are taken to strengthen the body’s immune response. And a certain time interval is needed between the second or third doses of vaccine to allow enough time for the body’s immune system to respond. In addition, the New Crown vaccine is relatively unique in that there is both a three-dose vaccine and a two-dose vaccine. The two-dose vaccine is an inactivated vaccine, which has the advantages of being relatively simple and efficient to produce and easy to store and transport, relatively short total vaccination time, and similar antigenicity to live viruses. However, the disadvantages are that the immunization route is relatively single in effect and antigenic damage may occur during production, making it unsuitable for large-scale production and more costly. In contrast, the three-dose New Crown vaccine is a recombinant protein vaccine, which is suitable for mass production, safe and relatively inexpensive because the complete virus is not required in the production process, but the disadvantage is that the total vaccination time is relatively longer. However, there is no significant difference in the effect of the two vaccines, so if the vaccinees are in a hurry, they can choose the two-dose vaccine, but both are safe and effective, so there is no need to compare their advantages and disadvantages too much.