Safety and Immunogenicity of the Recombinant Respiratory Syncytial Virus (RSV) Vaccine in Adults Aged 18 Years and Older

Inclusion Criteria:

1. Residents aged 18 years and older (at the time of screening), regardless of gender;

2. Participants can provide valid identification, voluntarily agree to participate inthe study, and sign the Informed Consent Form, and are able to attend all plannedfollow-up visits and comply with the protocol requirements;

3. Axillary temperature < 37.3°C on the day of enrollment;

4. Females of childbearing potential should use effective contraceptive measures onemonth before enrollment; females of childbearing potential (excluding those who haveundergone tubal ligation, bilateral oophorectomy, or hysterectomy) and maleparticipants should practice effective contraception and avoid pregnancy plans, aswell as sperm or egg donation plans from the time of enrollment until 6 months afterthe full course of vaccination. Effective contraceptive methods include oralcontraceptives (excluding emergency contraceptives), injectable or implantablecontraceptives, sustained-release local contraceptives, contraceptive patches,intrauterine devices, sterilization, abstinence, condoms, diaphragms, cervical caps,etc.

Exclusion Criteria:

1. Allergy to the investigational vaccine or its excipients, or a history ofanaphylactic shock or other serious adverse reactions to other vaccines;

2. Previous vaccination against Respiratory Syncytial Virus;

3. A confirmed diagnosis or etiological evidence of respiratory syncytial virusinfection and related diseases caused by the infection within 12 months beforeenrollment;

4. Has taken antipyretics, analgesics or anti-allergy drugs within 24 hours beforeenrollment;

5. Has received any vaccine within 14 days before vaccination, or have received a livevaccine within 28 days;

6. Has received blood or blood-related products, including immunoglobulin, within 3months prior to enrollment; or plan to use them during the study period;

7. Individual with the following diseases:

• Has acute diseases or are in the acute exacerbation period of chronic diseaseswithin 3 days before vaccination;

• Diagnosed with congenital malformations or developmental disorders, geneticdefects, severe malnutrition, etc.;

• History of congenital or acquired immunodeficiency or autoimmune diseases;

• Chronic administration (≥14 consecutive days) of corticosteroids (dose ≥ 20mg/day prednisone or equivalent dose) or other immunosuppressants within thepast 3 months, with the exception of inhaled or topical steroids, or short-termuse (<14 consecutive days) of oral corticosteroids;

• Neurological diseases or family history (seizures, epilepsy, encephalopathy,etc.); history of psychiatric disorders or family history;

• Asplenia or functional asplenia;

• Severe or uncontrolled or hospitalization-required cardiovascular diseases,diabetes, blood and lymphatic system diseases, immune system diseases, liverand kidney diseases, respiratory system diseases, metabolic and skeletal systemdiseases, or malignant tumors;

• Contraindications for intramuscular injection and blood drawing, such ascoagulation disorders, thrombosis or hemorrhagic diseases, or situationsrequiring continuous use of anticoagulants;

• Severe hypertension that cannot be controlled by medication (measured on-site:systolic blood pressure ≥ 160 mmHg and/or diastolic blood pressure ≥ 100 mmHg);

8. History of major surgery within 12 weeks prior to enrollment (as determined by theinvestigator), or not fully recovered from the surgery, or having plans for majorsurgery during the anticipated period of the subject's participation in the study;

9. History of long-term alcohol abuse and/or drug abuse;

10. Individual who is currently participating in other research or unregistered product (drugs, vaccines, or devices, etc.) clinical studies, or plan to participate inother clinical studies before the end of this clinical study;

11. Other conditions that may impact the subject's safety or influence the assessment ofvaccine response, as determined by the investigator;

12. Exclusion criteria for specific populations: lactating or pregnant women during theclinical research period, or women of childbearing age with a positive pregnancytest before vaccination.