A total of 112 participants will be enrolled in the study. All the participants have immunized with two doses of inactivated COVID-19 vaccine at least 6 months ago. The 98 participants will be inoculated with one dose COVID-19 messenger ribonucleic acid(mRNA) vaccine from Stemirna Therapeutics Co., Ltd and the others will be inoculated with one dose inactivated COVID-19 vaccine from institute of medical biology, Chinese academy of medical sciences(IMBCAMS). Before the inoculation, 14 days and 28 days after the immunization, blood samples will be taken for determination of neutralizing antibody and immunoglobulin G(IgG) antibody against severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) N protein and S protein (enzyme-linked immuno sorbent assay, ELISA method); and before the inoculation and 28 days after the immunization, blood samples will be taken for detecting specific T cells with the enzyme-linked immunospot(ELISPOT) assay with an aim to evaluate immunogenicity. Safety observations for all participants will be conducted from the inoculation to 28 days, and follow-up of severe adverse events (SAEs) will also be conducted from inoculation to at least 12 months to evaluate the safety of the investigational vaccine.
this is a voluntary, investigator-initiated, inactivated COVID-19 vaccine controlled clinical trial to evaluate the immunogenicity and safety of COVID-19 mRNA vaccine in adults aged 18 years and above which have immunized with two dose of inactivated COVID-19 vaccine at least 6 months ago.