Safety and Immunogenicity of SARS-CoV-2 Protein Subunit Recombinant Vaccine in Healthy Children

Inclusion Criteria: 1. Clinically healthy children aged 12-17 years. 2. Parent and/or legal guardian has been informed properly regarding the study and signed the informed consent form (and assent for subjects aged 12-17 years). 3. Parent and/or legal guardian will commit to comply with the instructions of the investigator and the schedule of the trial. Exclusion Criteria: 1. Subjects concomitantly enrolled or scheduled to be enrolled in another trial. 2. History of vaccination with any COVID-19 vaccine (based on anamnesis). 3. Subjects who have history of COVID-19 in the last 3 months (based on anamnesis). 4. Evolving mild, moderate or severe illness, especially infectious disease or fever (body temperature ≥37.5℃, measured with infrared thermometer/thermal gun). 5. History of asthma, history of allergy to vaccines or vaccine ingredients, and severe adverse reactions to vaccines, such as urticaria, dyspnea, and angioneurotic edema. 6. History of uncontrolled coagulopathy or blood disorders contraindicating intramuscular injection. 7. Patients with serious chronic diseases (serious cardiovascular diseases, uncontrolled hypertension and diabetes, liver and kidney diseases, malignant tumors, etc) which according to the investigator might interfere with the assessment of the trial objectives. 8. Subjects who have any history of confirmed or suspected immunosuppressive or immunodeficient state, or received in the previous 4 weeks a treatment likely to alter the immune response (intravenous immunoglobulins, blood-derived products or long-term corticosteroid therapy (\> 2 weeks)). 9. Subjects who have history of uncontrolled epilepsy or other progressive neurological disorders, such as Guillain-Barre Syndrome. 10. Subjects receive any vaccination (other than COVID-19 vaccine) within 1 month before and after IP immunization. 11. Female who are pregnant or planning to become pregnant during the study period (judged by self-report of subjects and urine pregnancy test results). 11\. Subjects plan to move from the study area before the end of study period.