The third injection of the new crown vaccine is generally referred to as booster injection, which is not mandatory in the country, but it is recommended for those who are eligible to receive the vaccination to receive the injection as early as possible, so as to strengthen the antibodies in the body. People aged 18 years and above who have completed two doses of inactivated vaccine and the second dose has been given 6 months ago are required to meet the above conditions before they can receive the third dose of XKV vaccine. However, there is no mandatory requirement for the third injection, but it is recommended for those who fulfill the requirements to receive the third injection as soon as possible, as it can strengthen the immunization. Antibodies to the previously injected inactivated vaccine will gradually fade after 6 months, and the third injection at this time will greatly increase the recipient’s antibody level, which is equivalent to 10 to 30 times the original antibody level. However, the antibody of the vaccine is not one hundred percent, and after timely vaccination, it is also necessary to strengthen the epidemic prevention and control measures.