This is a randomized, double-blind, parallel-controlled Phase I clinical trial of Adsorbed Tetanus Vaccine. Participants aged ≥18 years will receive one dose of the vaccine to evaluate its safety and immunogenicity.

This trial will adopt a randomized, double-blind, parallel-controlled design. A total of 80 participants aged ≥18 years will be enrolled, with 40 participants in the 18-59 years group and 40 participants in the ≥60 years group. Participants in each age group will be randomized at a 1:1 ratio into the investigational vaccine group and the control vaccine group to receive one dose of investigational vaccine or control vaccine. Participants aged 18-59 years will be enrolled first and will receive a 7-day safety observation after vaccination. If the trial suspension criteria are not met, enrollment of participants aged ≥60 years will be initiated subsequently.

All participants will be observed for adverse events (AEs) within 30 days after vaccination, and for serious adverse events (SAEs), adverse events of special interest (AESIs), and pregnancy events within 6 months after vaccination. In addition, all participants will undergo complete blood count, blood biochemistry and routine urinalysis tests before vaccination and on Day 3 after vaccination.

All participants will have peripheral venous blood samples collected before vaccination and on Day 30 after vaccination to determine serum tetanus antibody levels.

Inclusion Criteria:

1. Participants aged ≥ 18 years.
2. Able to provide valid personal identification.
3. Able to provide their own informed consent, voluntarily participate in the trial, and sign the informed consent form; able to use a thermometer and ruler, and complete diary/contact cards as required.
4. Able to comply with the trial protocol, attend scheduled examinations, and cooperate with follow-up visits.

Exclusion Criteria:

The following criteria will be assessed during screening/enrollment. Participants meeting any of the following conditions will be excluded from the trial. (Participants meeting only the exclusion criteria marked with an asterisk (*) may be rescheduled for screening.)

1. History of confirmed tetanus infection.

2. Receipt of tetanus vaccine or vaccines containing tetanus toxoid component (such as DTaP, DT, or vaccines using tetanus toxoid as carrier) within 10 years; or administration of tetanus immunoglobulin (human or animal origin) within 6 months.

3. Axillary temperature > 37.0 ℃ on the day of vaccination before inoculation*.

4. Abnormal laboratory findings in complete blood count, blood biochemistry and routine urinalysis during the screening period, which are judged to be clinically significant by the investigator.

5. Presence of any acute disease or acute exacerbation of chronic disease within 3 days before vaccination.

6. Receipt of the following medications or vaccines before vaccination*:

   • Have used antipyretic, analgesic or anti-allergic drugs within 3 days before vaccination;
   • Have received inactivated vaccines, subunit vaccines or other non-live vaccines within 7 days (inclusive);
   • Have received live attenuated vaccines within 14 days (inclusive);
   • Have used blood products including gamma globulin or immunoglobulin therapy within 3 months;
   • Have used long-term (continuous use ≥ 14 days) immunosuppressants or other immunomodulatory drugs (e.g., corticosteroids such as prednisone or similar drugs) within 6 months; however, topical medications (e.g., ointments, eye drops, inhalants or nasal sprays) are permitted, provided the dose should not exceed the recommended dose in the product labeling.

7. Positive urine pregnancy test, inability to rule out pregnancy before vaccination, or breastfeeding status; For women of childbearing potential who are pre-menopausal: last menstrual period more than 1 month ago, or plan to become pregnant within 6 months after enrollment (applicable only to female participants of childbearing potential).

8. History of severe allergic diseases or severe adverse reactions to vaccines (such as anaphylactic shock, allergic laryngeal edema, allergic purpura, local allergic necrosis reaction (Arthus reaction), severe urticaria, angioneurotic edema, etc.), or allergy to any component of the investigational vaccine.

9. History of confirmed thrombocytopenia or other coagulation disorders that may constitute a contraindication to intramuscular injection.

10. History of congenital or acquired immunodeficiency or autoimmune diseases, such as autoimmune diseases (e.g., systemic lupus erythematosus), immunodeficiency (e.g., acquired immunodeficiency syndrome), lymphoma, leukemia, rheumatoid arthritis, juvenile rheumatoid arthritis, inflammatory bowel disease, or other immune-related diseases or immunocompromised conditions that may interfere with trial evaluation as judged by the investigator.

11. Asplenia or functional asplenia, and asplenia or splenectomy caused by any conditions.

12. Presence of congenital malformations affecting organ function, developmental disorders, Down syndrome, sickle cell anemia, or any severe or potentially severe diseases that may interfere with trial completion; including but not limited to respiratory diseases such as asthma, uncontrolled hypertension (systolic blood pressure ≥ 160 mmHg and/or diastolic blood pressure ≥ 100 mmHg), pulmonary diseases, cardiovascular and cerebrovascular diseases, hepatic and renal diseases, malignant tumors, type I diabetes, uncontrolled type Ⅱ diabetes, infectious or allergic skin diseases.

13. History of neurological diseases such as epilepsy, Parkinson's disease, Guillain-Barré syndrome, convulsions (excluding simple febrile seizures), or progressive neurological disorders.

14. Previous or current history of psychiatric/psychological disorders including dementia, schizophrenia, depression, autism, delusional disorder, abulia, bipolar disorder, etc.

15. Currently participating in or planning to participate in other clinical trials during this trial period.

16. Plan to permanently move from the local area before the end of the trial, or plan to leave the local area for a long period that will affect scheduled trial visits.

17. Any other condition that may interfere with the trial evaluation as judged by the investigator.