inclusion criteria: * subjects of 18 years old and above who has completed basic immunization with recombinant novel coronavirus vaccine (cho cells) since 6 months (window period ± 1 month); * the subjects voluntarily participate in the study, sign an informed consent form, and can provide valid identification, understand and comply with the requirements of the trial protocol; * female subjects of childbearing age agree to take effective contraceptive measures from the start of the study to 1 month after vaccination.

inclusion criteria: * subjects of 18 years old and above who has completed basic immunization with recombinant novel coronavirus vaccine (cho cells) since 6 months (window period ± 1 month); * the subjects voluntarily participate in the study, sign an informed consent form, and can provide valid identification, understand and comply with the requirements of the trial protocol; * female subjects of childbearing age agree to take effective contraceptive measures from the start of the study to 1 month after vaccination.

inclusion criteria: subjects of 18 years old and above who has completed basic immunization with recombinant novel coronavirus vaccine (cho cells) since 6 months (window period ± 1 month); the subjects voluntarily participate in the study, sign an informed consent form, and can provide valid identification, understand and comply with the requirements of the trial protocol; female subjects of childbearing age agree to take effective contraceptive measures from the start of the study to 1 month after vaccination.

inclusion criteria: subjects of 18 years old and above who has completed basic immunization with recombinant novel coronavirus vaccine (cho cells) since 6 months (window period ± 1 month); the subjects voluntarily participate in the study, sign an informed consent form, and can provide valid identification, understand and comply with the requirements of the trial protocol; female subjects of childbearing age agree to take effective contraceptive measures from the start of the study to 1 month after vaccination.