A Real-world Study to Evaluate the Safety and Immunogenicity of a Third-dose Booster After Two Doses of an Inactivated COVID-19 Vaccine

Inclusion Criteria: * Age \>18 years old, gender is not limited; * Subjects who completed the second dose of COVID-19 inactivated vaccine for more than 6 months and received the third dose of the same vaccine Exclusion Criteria: * allergic to the active ingredients of the SARS-CoV-2 vaccine, any of the inactive ingredients, the substances used in the production process, or those who have had allergies during previous vaccination of similar vaccines; * those who have had severe allergic reactions to vaccines in the past (such as acute allergic reactions, angioedema, respiratory Difficulties, urticaria, angioedema or abdominal pain); * Receiving other research drugs within 3 months ;participating in other research vaccines Or subjects in clinical trials of research drugs; * other conditions that the investigator judges are not suitable for this clinical trial;