A Study to Evaluate Efficacy, Immunogenicity and Safety of a Recombinant Respiratory Syncytial Virus Vaccine in Older Adults Aged 60 Years and Older

This is a randomized, observer-blinded, placebo-controlled Phase III clinical trial to evaluate efficacy, immunogenicity and safety of the Respiratory Syncytial Virus (RSV) Vaccine, LYB005 in participants aged 60 years and older.

Inclusion Criteria: * 1\. A male or female participant aged 60 years and above； 2. Participants can provide valid identification, voluntarily agree to participate in the study, and sign the Informed Consent Form, and are able to attend all planned follow-up visits and comply with the protocol requirements； 3. Axillary temperature ≤ 37.0°C on the day of enrollment; 4. Female participants should have been menopausal or have undergone sterilization surgery; Menopause is defined as the absence of menstruation for at least 12 consecutive months without alternative medical measures; sterilization surgeries include bilateral tubal ligation or bilateral oophorectomy or hysterectomy; Male participants must not plan to father a child from the time of screening until 30 days after vaccination; 5. Participants in the trial who were judged by the researchers to be healthy or have stable health conditions. \[Stable health condition: This refers to having a chronic disease and maintaining a stable condition within the three months prior to enrollment irrespective of receipt of specific treatment, such as diabetes, hypertension, chronic obstructive pulmonary disease, and asthma. If the researcher determines that the condition is stable, participation in this trial will be permitted.\]. Exclusion Criteria: * 1\. Participants who are known to be allergic to any of the components contained in the test vaccine (e.g., sucrose, polysorbate 20, sodium dihydrogen phosphate dihydrate, and disodium hydrogen phosphate dihydrate.); A history of severe allergic reactions or serious adverse reactions to any vaccine; 2. A confirmed diagnosis or etiological evidence of respiratory syncytial virus infection and related diseases caused by the infection within 12 months before enrollment (confirmed by RT-PCR, RSV-Ab, etc.); 3. Have received or plan to receive any marketed or experimental RSV vaccine/RSV prophylactic medication; 4. Has taken antipyretics, analgesics (except for medications used for underlying conditions that, in the investigator's judgment, are unlikely to affect study outcomes, such as enteric-coated aspirin for the prevention of cardiovascular and cerebrovascular diseases.) or anti-allergy drugs within 3 days before enrollment; 5. Receipt of any non-live vaccine within 14 days prior to enrollment, or any live or nucleic acid vaccine within 28 days prior to enrollment; 6. Any non-specific immunoglobulins and/or blood products containing non-specific immunoglobulins (such as whole blood, plasma) have been used within 3 months prior to enrollment or are planned to be used during the trial; 7. Individual with the following diseases: ①Has acute diseases or are in the acute exacerbation period of chronic diseases within 3 days before vaccination; ②Individual with active tuberculosis or currently undergoing treatment for tuberculosis; ③History of congenital or acquired immunodeficiency or autoimmune diseases; Chronic administration (≥14 consecutive days) of corticosteroids (dose ≥ 20 mg/day prednisone or equivalent dose) or other immunomodulatory medications within the past 3 months, currently using or planning to use a long-acting immunomodulatory agent (e.g., infliximab), with the exception of inhaled or topical steroids, or short-term use (\