This phase 2 study in China will evaluate the immunogenicity and safety of the Recombinant Zoster Vaccine, LYB004 in adults aged 40 years and older.

A randomized, observer-blinded, parallel-controlled trial will be conducted to observe the immunogenicity and safety of LYB004 in adults aged 40 years and older. A total of 840 participants aged 40 years and older will be enrolled. Four formulations of LYB004 will be provided: two dose levels of antigen and two dose levels of adjuvant. Participants aged 40-49 years old will randomly receive four investigational vaccines and the placebo in a 2:2:2:2:1 ratio. Participants aged 50 years and older will randomly receive four investigational vaccines, positive control and the placebo in a 2:2:2:2:2:1 ratio.

Inclusion Criteria:

1. Residents aged 40 years and older (at the time of screening), regardless of gender;
2. Participants can provide valid identification, voluntarily agree to participate in the study, and sign the Informed Consent Form;
3. Participants are able to attend all planned follow-up visits and comply with the protocol requirements;
4. Females of childbearing potential should use effective contraceptive measures one month before enrollment; females of childbearing potential (excluding those who have undergone tubal ligation, bilateral oophorectomy, or hysterectomy) and male participants should practice effective contraception and avoid pregnancy plans, as well as sperm or egg donation plans from the time of enrollment until 6 months after the full course of vaccination. Effective contraceptive methods include oral contraceptives (excluding emergency contraceptives), injectable or implantable contraceptives, sustained-release local contraceptives, contraceptive patches, intrauterine devices, sterilization, abstinence, condoms, diaphragms, cervical caps, etc.

Exclusion Criteria:

1. Axillary temperature ≥ 37.0°C;
2. History of herpes zoster before vaccination with the investigational vaccine;
3. Previous vaccination against HZ or varicella;
4. Has had close contact with patients with varicella/herpes zoster within 6 months before vaccination with the investigational vaccine;
5. Has received any vaccine within 14 days before vaccination, or have received a live vaccine within 28 days;
6. Those who have received blood or blood-related products, including immunoglobulins, within 3 months before the first dose of vaccination, or have planned to use them during the study period;
7. Individual with the following diseases: ① Have acute diseases or are in the acute exacerbation period of chronic diseases, or take antipyretic, analgesic, and anti-allergic drugs within 3 days before vaccination; ② Allergies to any component of the study vaccine, or have a history of severe allergic reactions to any vaccination; ③ History of convulsions, epilepsy, encephalopathy (such as congenital brain dysplasia, brain trauma, brain tumors, cerebral hemorrhage, cerebral infarction, brain infection, chemical poisoning, etc. causing brain nerve tissue damage, etc.) and mental illness, or a family history of mental illness; ④ Asplenia, or functional asplenia; ⑤Primary or secondary immunodeficiency, or diagnosed with congenital or acquired immunodeficiency, human immunodeficiency virus infection, lymphoma, leukemia, systemic lupus erythematosus, rheumatoid arthritis, juvenile rheumatoid arthritis, inflammatory bowel disease, or other autoimmune diseases; ⑥ Chronic administration (≥14 consecutive days) of glucocorticoid (reference value for dose: ≥ 2mg/kg/day or ≥ 20mg/day prednisone or equivalent) or other immunosuppressive agents within the past 3 months, with the exception of inhaled or topical steroids, or short-term use (<14 consecutive days) of oral corticosteroids; ⑦ Severe cardiovascular diseases (pulmonary heart disease, pulmonary edema, etc.), severe liver and kidney diseases, complicated diabetes; ⑧ History of thrombocytopenia or other coagulation disorders that may contraindicate intramuscular injection;⑨Severe hypertension that cannot be controlled by medication (on-site measurement: systolic blood pressure ≥ 140mmHg and/or diastolic blood pressure ≥ 90mmHg);
8. Those tested positive for antibodies to the Human Immunodeficiency Virus (HIV) at screening.;
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 in other clinical studies before the end of this clinical study;
11. Exclusion criteria for specific populations: lactating or pregnant women during the clinical research period, or women of childbearing age with a positive pregnancy test before vaccination;
12. Other conditions that may impact the subject's safety or influence the assessment of vaccine response, as determined by the investigator.