inclusion criteria: * adults aged 18-45; * proven legal identity; * the subjects can understand and voluntarily sign the informed consent form and be willing to complete the study in accordance with the study plan; * have completed two doses of sars-cov-2 inactivated vaccine vaccination for 6 to 8 months(the interval between the two doses vaccine of primary immunization is 21\~35 days, and the two doses vaccine of primary immunization should be manufactured by the same manufactures).

inclusion criteria: * adults aged 18-45; * proven legal identity; * the subjects can understand and voluntarily sign the informed consent form and be willing to complete the study in accordance with the study plan; * have completed two doses of sars-cov-2 inactivated vaccine vaccination for 6 to 8 months(the interval between the two doses vaccine of primary immunization is 21\~35 days, and the two doses vaccine of primary immunization should be manufactured by the same manufactures).

inclusion criteria: adults aged 18-45; proven legal identity; the subjects can understand and voluntarily sign the informed consent form and be willing to complete the study in accordance with the study plan; have completed two doses of sars-cov-2 inactivated vaccine vaccination for 6 to 8 months(the interval between the two doses vaccine of primary immunization is 21~35 days, and the two doses vaccine of primary immunization should be manufactured by the same manufactures).

inclusion criteria: adults aged 18-45; proven legal identity; the subjects can understand and voluntarily sign the informed consent form and be willing to complete the study in accordance with the study plan; have completed two doses of sars-cov-2 inactivated vaccine vaccination for 6 to 8 months(the interval between the two doses vaccine of primary immunization is 21~35 days, and the two doses vaccine of primary immunization should be manufactured by the same manufactures).