This clinical trial included two parts, Part A and Part B. The goal of Part A is to evaluate the safety and preliminary immunogenicity of the lyophilized herpes zoster virus mRNA vaccine (HZ mRNA vaccine) in healthy populations aged 40 years and older. The goal of Part B is to select the optimal dosage and schedule in healthy populations aged 50 years and older to support next further study.

This is a randomized, double-blind, controlled study. Part A employed sequential enrollment by age and dosage. All participants received two doses of the study vaccine. Safety observation conducted throughout the study. Humoral and celluar immunity were evaluated.

In Part B, participants randomly received either different dosage study vaccine or active controlled vaccine, with different immunization schedule. Safety observation conducted throughout the study. Humoral and celluar immunity were evaluated. Immune persistence was also evaluated at multiple timepoints after vaccination.

Inclusion Criteria:

• Phase I: Age ≥ 40 years; Phase II: Age ≥ 50 years;
• Participants are able to understand and voluntarily sign the informed consent form;
• Able to provide legal identification;
• Participants of childbearing potential and their sexual partners agree to voluntarily adopt effective contraceptive measures from the signing of the informed consent form until 6 months after the last dose of the investigational vaccine, with no plans for sperm or egg donation;
• Agree to comply with the visit schedule, sample collection, vaccination, and other trial procedures throughout the study period, and remain accessible at all times during the trial.

Exclusion Criteria:

• History of chickenpox or herpes zoster in adulthood;
• History of chickenpox or herpes zoster vaccination (including administration of registered products or participation in clinical trials of chickenpox or herpes zoster vaccines);
• Close contact with patients infected with chickenpox or herpes zoster within the past 30 days;
• Clinically significant abnormalities in protocol-specified clinical laboratory tests prior to vaccination (applicable to Phase I clinical trials only):

A. Hematological parameters: White blood cell count (WBC), hemoglobin (Hb), platelet count (Plt); B. Blood biochemical parameters: Alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL), fasting blood glucose (Glu), creatinine (CR); C. Urinalysis parameter: Urine protein (PRO); D. Coagulation parameters: Prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen (Fib), international normalized ratio (INR); E. 12-lead electrocardiogram (ECG).

• Poorly controlled chronic diseases or significant medical history, including but not limited to cardiovascular diseases (e.g., poorly controlled hypertension defined as systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg for participants aged 40-59 years prior to enrollment, or systolic blood pressure ≥150 mmHg and/or diastolic blood pressure ≥100 mmHg for participants aged ≥60 years), metabolic disorders (e.g., poorly controlled diabetes), hematological diseases, hepatic or renal diseases, digestive system diseases, respiratory system diseases, history of major organ transplantation, or malignancy within the past five years;
• History of myocarditis, pericarditis, or idiopathic cardiomyopathy, or any condition that increases the risk of myocarditis or pericarditis;
• Autoimmune diseases, immunodeficiency diseases, or family history thereof (including but not limited to psoriasis, systemic lupus erythematosus, ankylosing spondylitis, autoimmune thyroid diseases, acute disseminated encephalomyelitis, facial paralysis, hypersensitivity reactions, polymyalgia rheumatica, rheumatoid arthritis, Guillain-Barré syndrome, asplenia, functional asplenia, HIV infection);
• Coagulation disorders (e.g., coagulation factor deficiencies, platelet abnormalities, or other coagulopathies);
• Current or previous severe neurological disorders (epilepsy, convulsions, or seizures) or psychiatric illnesses, or family history of psychiatric disorders;
• Acute illnesses or acute exacerbations of chronic diseases within the past 7 days, or known or suspected active infections;
• Immunosuppressive therapy or other immunomodulatory treatments (prednisone ≥20 mg/day or equivalent for >14 days), cytotoxic therapy within the past 6 months, or planned use during the trial;
• Administration of immunoglobulins or other blood products within the past 3 months (use of hepatitis B immunoglobulin within the past 1 month), or planned use during the trial;
• Participation in other clinical studies within the past 30 days or planned participation during this trial;
• Vaccination with live-attenuated vaccines or nucleic acid vaccines within the past 28 days, or vaccination with subunit, inactivated, or other types of vaccines within the past 14 days;
• Known allergy to vaccines or vaccine components, such as urticaria, dyspnea, or angioedema following vaccination;
• Pregnancy, lactation, or positive urine pregnancy test in female participants;
• Fever (axillary temperature ≥37.3°C) within 3 days prior to vaccination or use of antipyretics, analgesics, or antihistamines (e.g., acetaminophen, ibuprofen, loratadine, cetirizine, etc.) as reported during inquiry;
• Physical examination deemed unsatisfactory on the day of planned vaccination;
• Skin lesions, inflammation, ulcers, rashes, scars, or other conditions at the target injection site that may interfere with administration or local reaction assessment;
• Any other factors deemed by the investigator to render the participant unsuitable for participation in the clinical trial.