A Study to Evaluate the Safety and Immunogenicity of Omicron COVID-19 Vaccine (Vero Cell), Inactivated in Population 18 Years Old of Age and Above

This is a non-randomized, open-label, externally controlled study to evaluate the safety and immnunogenicity of the Omicron COVID-19 Vaccine (Vero Cell), Inactivated in population aged 18 years old and above with no vaccination history of the COVID-19 vaccine. 200 health subjects will be recruited in this study, including 150 aged 18-59 years old and 50 aged 60 years old and above. All subjects will be received 2 doses of Omicron COVID-19 Vaccine (Vero Cell), Inactivated according to the immunization schedule of 0, 21-28 days. The change in neutralizing antibody level at 28 days after the second dose was used to determine whether to receive a further booster dose for ≥3 months. The occurrence of adverse events within 28 days and serious adverse events within 6 months after vaccination will be observed. In addition, blood samples will be collected on Day 0 before vaccination,Day 14 after dose 1, before dose 2 and on day 14, 28 and month 3, 6, 9, 12 after dose 2. Serum antibody levels, cellular immune responses will be analyzed.