The purpose of the sutdy is to evaluate efficacy, safety and immunogenicity of Recombinant Zoster Vaccine (CHO Cell) with 2 doses at 2-month interval in adults aged 40 years and older.

A total of 25000 adults aged 40 years and older will be enrolled, stratified into 40-49, 50-59, 60-69 and ≥70 years of age. All subjects will randomly receive investigational vaccine or placebo at a ratio of 1:1. Efficacy and safety will be assessed in all subjects, while immunogenicity will be assessed in a subset of 1250 subjests in a selected trial site.

Inclusion Criteria:

1. A male or famale permanent resident aged 40 years and older at enrollment, with valid identity;
2. Subjects voluntarily agree to participate in the study and signed an informed consent;
3. Be able to understand clinical trials, participate in all scheduled visits and comply with the protocol requirements(e.g. completion of the diary cards/questionnaires, return for follow-up visits, have regular contact to allow evaluation during the study);
4. Women of childbearing potential plan to aviod pregnancy and are willing to use effcetive contraception(e.g. oral contraceptive pills, injectable progestogen, percutaneous contraceptive patches, implants of levonorgestrel, intrauterine device, female and male sterilization or abstinence) within 12 months after the last vaccination, and the uses of the rhythm method alone, withdrawal alone, and emergency contraception, are not acceptable.

Exclusion Criteria:

1. Axillary temperature>37.0℃;
2. Current or history of herpes zoster;
3. Previous vaccination against varicella or herpes zoster (either registered product or participation in a previous vaccine study);
4. Pregnant (urine pregnancy test was positive) or lactating female;
5. Receipt of live vaccine within 28 days, or any other vaccine within 14 days prior to vaccination;
6. Receipt of immunoglobulin or intravenous immunoglobulin during 3 months before vaccination to 1 month post the last vaccination;
7. Acute diseases or acute exacerbation of chronic disease within 3 days before vaccination;
8. Receipt of antipyretic, analgesic and allergy drugs within 3 days before vaccination, except enteric-coated aspirin for cardiovascular diseases prevention;
9. 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) to any previous vaccination;
10. Allergy to aminoglycoside antibiotics;
11. History of convulsions, epilepsy, encephalopathy (e.g. congenital brain dysplasia, brain trauma, brain tumor, cerebral hemorrhage, cerebral infarction, brain infection disease, nerve tissue damage caused by chemical drug poisoning), mental illness and family history, and other serious neurological diseases;
12. Asplenia or functional asplenia, or splenectomy caused by any condition;
13. Primary or secondary impairment of immune function, diagnosed congenital or acquired immunodeficiency, human immunodeficiency virus (HIV) infection, lymphoma, leukemia, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease or other autoimmune diseases;
14. Receipt of immunosuppressive therapy (e.g. long-term use of systemic glucocorticoid ≥14 days, dose ≥2mg/kg/day or ≥20mg/day prednisone or equivalent dose) during 6 months before vaccination to 1 minth post the last vaccination, but inhaled, nasal spray, intra-articular, eyedrops, ointment and other topical steroids are acceptable;
15. Receipt of long-acting immune-modifying drugs (e.g. Infliximab) within 6 months before vaccination or during the study period;
16. Severe chronic disease, including but not limited to, severe cardiovascular disease(e.g. Pulmonary heart disease, Pulmonary Edema), severe liver or kidney disease, or diabetes with complication;
17. History of thrombocytopenia or other coagulation disorders, which may cause intramuscular injection contraindications;
18. Abnormal and uncontrlled blood pressure during physical examination before vaccination (for subjects aged 40-59: systolic pressure ≥ 140 mmHg and/or diastolic pressure ≥ 90 mmHg; for subjects aged ≥60, systolic pressure ≥ 150 mmHg and/or diastolic pressure ≥ 100 mmHg);
19. History of drug abuse (narcotic drugs, psychotropic drugs);
20. Current skin infections, in the opinion of the investigator, might interfere with the efficacy evaluation;
21. Current or history of malignant tumors, except papillary thyroid carcinoma;
22. Receipt of investigational products (drugs or vaccines) within 6 months before vaccination;
23. Planned participation in another clinical study during the study period;
24. Any condition that, in the opinion the investigator, may affect the safety of the subject or the evaluation of the study results.