Influenza Vaccine (Split Virion), Inactivated, Quadrivalent in Pregnant Women

Inclusion Criteria:

1. Pregnant women aged 18 to 39 years in good health or medically stable.

2. Gestational age of 20 to 32 weeks, based on last menstrual period, early or lateultrasound dating.

3. The participant was tested negative for HIV, Syphilis, Hepatitis B, Hepatitis Cinfection according to medical records or rapid tests.

4. Participants should provide verifiable identification.

5. Participants are able to understand and sign the informed consent form voluntarily;

6. Participants are willing and able to adhere to visit schedules and all studyrequirements.

Exclusion Criteria:

1. Receipt of any seasonal influenza vaccine within 6 months prior to enrollment, orplans to receive other influenza vaccines during the study;

2. Participants with previous or concurrent dangerous pregnancy complications such asgestational diabetes mellitus (GDM), pregnant induced hypertension, preeclampsia andknown uterine anomaly;

3. History of preterm delivery, or spontaneous abortion;

4. Known fetal congenital anomaly, e.g. genetic abnormality or major congenitalmalformation based on antenatal ultrasound;

5. Signs or symptoms of active preterm labor, defined as regular uterine contractionswith cervical change (dilation/effacement);

6. History of Guillain-Barré syndrome within 6 weeks of a prior dose of any influenzavaccine;

7. Received any vaccine in the 4 weeks prior to study vaccination, or plans to receiveany vaccine within 4 weeks after study vaccination;

8. Serious allergic reaction or other serious adverse reaction to any influenzavaccines or their components;

9. Autoimmune diseases, immunodeficiency, any immunosuppressant within 6 months priorto vaccination (≥ 20mg/day prednisone or equivalent, but corticosteroid spraytherapy for allergic rhinitis and surface corticosteroid therapy for acutenon-concurrent dermatitis are permitted) or cytotoxic therapy, or plans for suchtreatment during the study;

10. Diagnosed abnormal coagulation function (e.g., coagulation factor deficiency,coagulation disorders, or platelet abnormalities), or obvious bruising followingvenipuncture;

11. Significant chronic diseases that, in the judgement of the investigator, mightinterfere with the study (may include, but are not limited to cardiovasculardisease, liver or kidney disorders, HIV infection or malignant tumor);

12. Current or history of severe neurological diseases (such as epilepsy, convulsions orseizures) or psychiatric disorders, or family history of psychiatric disorders;

13. Acute diseases or acute stage of chronic diseases within 7 days prior tovaccination;

14. Receipt of blood, blood-derived products or immunoglobulins within 3 months prior tovaccination or plans for such treatment in the study;

15. Alcoholism or history of drug abuse;

16. Receipt of other investigational drugs/vaccines within 30 days prior to enrollment,or plan to receive investigational drugs/vaccines during the study period;

17. Fever on vaccination day, with axillary temperature ≥ 37.3°C pre-vaccination;

18. Any other factors which are unsuitable for participation in the clinical trial asjudged by the investigator.