Safety and Immunogenicity of Recombinant RSV Vaccine (CHO Cell) in Healthy Subjects Aged 18 Years and Above

Inclusion Criteria:

1. A male or female, in the opinion of the investigator, aged 18 and older for phase 1and aged 50 and older for phase 2 at the time of the enrollment;

2. Be able to understand the trial procedures, risks and benefits and voluntarily agreeto participate in the study and signed an informed consent;

3. Be able to participate in all scheduled visits and comply with the protocolrequirements;

4. Women of childbearing potential are willing to use effective contraception (e.g.oral contraceptives, injectable progestogen, implants of levonorgestrel,percutaneous contraceptive patches, intrauterine device (IUD), female and malesterilization, abstinence, condoms, or diaphragms), and the rhythm method,withdrawal and emergency contraception pills are not acceptable;

5. Subjects with stable conditions considered by the investigator.

Exclusion Criteria:

1. Axillary temperature>37.0℃;

2. History of RSV infection within 6 months before enrollment;

3. New onset of respiratory tract infection symptoms like cough, sputum, shortness ofbreath, wheezing, fever, runny nose or nasal congestion within 7 days beforeenrollment;

4. Acute diseases or acute exacerbation of chronic disease within 3 days beforevaccination;

5. A known allergy to any components of the study vaccine, or history of severe allergy (e.g. anaphylactic shock, allergic laryngeal edema, anaphylactoid purpura,thrombocytopenic purpura, Arthus reaction, severe urticaria) or serious adversereactions to any previous vaccination or drug use;

6. Pregnant (urine pregnancy test was positive) or lactating female, or plannedpregnancy within 12 months after vaccination;

7. Any confirmed or suspected immunosuppressive or immunodeficient condition due todiseases or immunosuppressive therapy, based on medical history and physicalexamination;

8. Serious or unstable chronic illness, including but not limit to cardiovasculardiseases (such as uncontrolled hypertension, coronary heart disease, myocarditis,pericarditis), metabolic diseases (such as poorly controlled diabetes),hematological diseases (such as severe anemia, hemophilia), liver and kidneydiseases, digestive diseases, respiratory diseases (such as chronic obstructivepulmonary disease, active tuberculosis, other severe respiratory diseases ),malignant tumor, major functional organ transplantation history;

9. Significant underlying illness that in the opinion of the investigator would beexpected to prevent completion of the study;

10. History of thrombocytopenia or other coagulation disorders;

11. History of convulsions, epilepsy, congenital brain dysplasia, mental illness orfamily history, or history of brain nerve tissue damage due to other severeneurological disorders(e.g. brain tumor, cerebral hemorrhage, cerebral infarction,brain infection disease, chemical drug poisoning);

12. History of cognitive dysfunction, or any moderate or severe cognitive impairment;

13. Asplenia or functional asplenia, or autoimmune thyroid diseases, such as Hashimotothyroiditis, toxic diffuse goiter;

14. Receipt of live vaccine within 28 days, or any other vaccine within 14 days prior tovaccination;

15. Previous vaccination with an RSV vaccine;

16. Administration of long-acting immune-modifying drugs(e.g. Infliximab) or plannedadministration at any time during the study period;

17. Administration of immunoglobulins and/or any blood products during the periodstarting 3 months before vaccination or planned administration during the studyperiod;

18. Chronic administration of immunosuppressants or other immune-modifying drugs (suchas long-term use of systemic glucocorticoid ≥14 days, ≥20mg/day prednisone orequivalent dose) during the period starting 3 months before vaccination or plannedadministration during the study period, but topical steroids(e.g. ointment, eyedrops, inhalants, nasal sprays) that do not exceed the dosage recommended in theinstructions or have any systemic signs are acceptable;

19. History of alcohol or drug abuse;

20. Concurrently participating in another clinical study, at any time during the studyperiod, in which the subject has been or will be exposed to an investigational or anon-investigational vaccine/product;

21. Planned move to a location that will prohibit participating in the trial until studyend;

22. At screening: Any laboratory test results(hematology, clinical chemistry,coagulation function, or urinalysis) abnormal and clinically significant in thejudgment of the investigator (Only for phase 1);

23. At screening: Any electrocardiogram abnormal and clinically significant in thejudgment of the investigator (Only for phase 1);

24. Any condition that, in the opinion the investigator, may affect the safety of thesubject or the evaluation of the study results.