A Phase III Clinical Trial to Evaluate the Protection Efficacy, Safety and Immunogenicity of One Dose of RQ3013 in Population Aged 18-59 Years and above Who Have Received 3 Doses of COVID-19 Inactivated Vaccine

INTERVENTION: study group:Study Vaccine Administration;control group:Control Vaccine Administration; CONDITION: Novel Coronavirus Pneumonia (COVID‐19) PRIMARY OUTCOME: Person‐year incidence rate of Symptomatic COVID‐19 ; SECONDARY OUTCOME: Live virus neutralizing antibody against current major SARS‐CoV‐2 VOC;S protein specific IgG antibody against SARS‐CoV‐2 Omicron strain; INCLUSION CRITERIA: Subjects shall meet all of the following INCLUSION CRITERIA: (1) Healthy adults aged =18 years and are able to provide legal identity certificate. Both male and female can be included. (2) The subjects shall fully understand the content of the informed consent form and the characteristics of the investigational vaccine, voluntarily sign the informed consent form, as well as have the ability to use thermometer, scale and fill in diary card and contact card as required. (3) The subjects shall be able to communicate well with the investigators, as well as understand and comply with the requirements of this study. (4) Subjects had been vaccinated with 3 doses of inactivated COVID‐19 vaccines at least 6 months ago of the third dose. (5) There is risk of SARS‐CoV‐2 infection due to regional, occupational, activity, environmental and other factors. (6) Healthy subjects or those with underlying disease but in stable control [in a stable state without