This project is a prospective observational real-world study, recruiting and screening subjects who have completed 2 doses of the COVID-19 vaccine for more than 6 months and receive the third dose of the vaccine voluntarily into the clinical cohort of this study. Subjects received a third dose of the COVID-19 vaccine will be enrolled in the study and followed up for 1 year at baseline (day 0) before vaccine injection, 28 days after injection, 90 days, 270 days after injection. On the 365th day, blood samples were collected for the detection of anti-SARS-CoV-2 antibodies and other related indicators to evaluate the immune protection effect.

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;

Recruit and screen subjects who have completed 2 doses of the new coronavirus vaccine for more than 6 months and voluntarily receive a third dose of the vaccine