A Phase IV Clinical Trial of Influenza Vaccine (Split Virion), Inactivatedin (Anflu®) Pregnant Women (AnFLU-PREG)

A Phase IV, Randomized, Double-blind, Positive-controlled , Multicenter Clinical Trial to Evaluate the Immunogenicity and Safety of Influenza Vaccine (Split Virion) , Inactivated (Anflu®) in Pregnant Women

A phase IV clinical trial of Influenza Vaccine (Split Virion), Inactivated (Anflu®) developed by Sinovac Biotech Co., Ltd will be conducted in pregnant women.

A total of 150 healthy pregnant women aged 18~45 years at 22 to 34 weeks (+6 days) of pregnancy will be enrolled. All participants will be randomized to test group and control group in a ratio of 2:1 and receive one dose of vaccine (0.5 mL) of Sinovac Influenza Vaccine (Split Virion) , Inactivated (Anflu®) or Sanofi VAXIGRIP®, respectively.

Study Overview

• Status: Not yet recruiting
• Conditions: Influenza
• Intervention / Treatment: Biological: Anflu®; Biological: Vaxigrip®

Detailed Description

A phase IV clinical trial of Influenza Vaccine (Split Virion), Inactivated (Anflu®) developed by Sinovac Biotech Co., Ltd will be conducted in Chinese pregnant women.

A total of 150 healthy pregnant women aged 18~45 years at 22 to 34 weeks (+6 days) of pregnancy will be enrolled.The trial is a randomized, double-blind, positive controlled study to evaluate the immunogenicity and safety of Influenza Vaccine (Split Virion) ,Inactivated (Anflu®) manufactured by Sinovac. The active control vaccine is VAXIGRIP® manufactured by Sanofi.

For immunogenicity assessment, blood samples will be collected from participants prior to vaccination, 28 days post-vaccination, and at the end of pregnancy (at delivery) to evaluate antibody levels in pregnant women following influenza vaccination. Additionally, the cord blood samples will be collected at delivery to assess transplacental antibody transfer to the fetus. Antibodies will be tested using the hemagglutination-inhibition (HI) assay.

For safety assessment, any immediate adverse events within 30 minutes after vaccine administration, solicited local and systemic adverse events within 7 days and unsolicited adverse events within 28 days will be collected. Serious adverse events will be collected from the time of informed consent signature until 3 months after delivery (or until 3 months after the event if pregnancy termination occurs). Pregnancy and neonatal outcomes will be collected by medical record review .

• Study Type: Interventional
• Enrollment (Estimated): 150
• Phase: Phase 4

Contacts and Locations

• Study Contact: Name: Qi Hongbo; Phone Number: 13808376116; Email: qihongbo@cqmu.edu.cn

Study Locations

• China
  • Changsha, China
    • Hunan Provincial Maternal and Child Health Care Hospital
    • Contact: Tang Yabing
  • Chengdu, China
    • Chengdu Women's and Children's Central Hospital
    • Contact: Lai Fan
  • Chongqing, China
    • The First Affiliated Hospital of Chongqing Medical University
    • Contact: Qi Hongbo
  • Guangzhou, China
    • Nanfang Hospital, Southern Medical University
    • Contact: Huang Liping
  • Nanjing, China
    • Nanjing Drum Tower Hospita
    • Contact: Li Jie
  • Wuhan, China
    • Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology
    • Contact: Feng Ling

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 45 years (Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: Female

Description

Inclusion Criteria:

1. Healthy pregnant women aged 18 to 45 years (inclusive) with stable health status, at 22 to 34 weeks (+6 days) of gestation. Gestational age is determined based on early ultrasound examination, or based on the last menstrual period if early ultrasound is unavailable.
2. Participants are able to understand and sign the informed consent form voluntarily;
3. Participants are willing and able to adhere to visit schedules and maintain accessible contact throughout the study period;
4. Participants should provide verifiable identification;
5. Have a singleton pregnancy;
6. Have normal non-invasive prenatal DNA test and systematic ultrasound results during the current pregnancy; normal amniocentesis results are required if the test has been performed.

Exclusion Criteria:

1. Have a history of two or more preterm deliveries (delivery before 37 weeks of gestation), previous infants with low birth weight (birth weight <2500 g), or a history of neonatal asphyxia or neonatal neurological damage;
2. Have a history of multiple unexplained spontaneous abortions;
3. Have received any influenza vaccine or the influenza vaccine for the current influenza season within 6 months prior to enrollment, or plan to receive influenza vaccination during the study period.
4. Have suffered from seasonal influenza within 6 months prior to enrollment.
5. Have a history of Guillain-Barré syndrome within 6 weeks after previous influenza vaccination.
6. Have allergic reactions or other severe adverse reactions to any influenza vaccine or its components.
7. Have severe autoimmune diseases or immunodeficiency diseases (including but not limited to active systemic lupus erythematosus, rheumatoid arthritis, asplenia, functional asplenia, and HIV infection) and are judged unsuitable for vaccination by the investigator.
8. Abnormal coagulation function (such as coagulation factor deficiency, coagulation disorders or platelet abnormalities).
9. Have severe chronic diseases (including but not limited to cardiovascular diseases, partial liver diseases, renal diseases or malignant tumors) that may interfere with the study as judged by the investigator.
10. Have a current or previous history of severe neurological diseases (epilepsy, convulsions) or psychiatric disorders, or have a family history of psychiatric disorders.
11. Received corticosteroids (adult prednisone ≥20 mg/day or equivalent) or other immunosuppressants for ≥14 days, or cytotoxic therapy within 6 months prior to vaccination, or plan to receive such therapy during the study period.
12. Received immunoglobulins or other blood products within 3 months prior to vaccination, or plan to receive such products during the study period.
13. Received any vaccine within 28 days prior to study vaccination, or plan to receive any vaccine within 28 days after study vaccination.
14. Have enrolled in other clinical trials of investigational drugs or vaccines during the follow-up period, or plan to receive investigational drugs or vaccines during the study period.
15. Have acute diseases or acute exacerbation of chronic diseases within 7 days before vaccination.
16. Have fever on the scheduled vaccination day with an axillary temperature ≥37.3 °C before vaccination.
17. Have clinically significant abnormal laboratory findings as judged by the investigator, or meet any of the following laboratory criteria: a) White blood cell count >15.0×10^9/L; b) Neutrophil percentage >85%; c) Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >2 times the upper limit of normal (2×ULN); d) Total bilirubin >2 times the upper limit of normal (2×ULN).
18. Any other factors which are unsuitable for participation in the clinical trial as judged by the investigator.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Test Group; 100 participants will receive one dose of vaccine (0.5 mL) of Sinovac Influenza Vaccine (Split Virion) Inactivated (Anflu®) . Route of administration is intramuscular injection at deltoid muscle of upper arm.Immunization schedule is 1 dose	Biological: Anflu®; Participants will receive one dose of Sinovac Anflu® .
Active Comparator: Control Group; 50 participants will receive one dose of vaccine (0.5 mL) of VAXIGRIP® manufactured by Sanofi. Route of administration is intramuscular injection at deltoid muscle of upper arm.Immunization schedule is 1 dose	Biological: Vaxigrip®; Participants will receive one dose of Sanofi Vaxigrip®.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
The seroconversion rates (SCRs) of hemagglutination inhibition (HI) antibodies at day 28 ,as measured by HAI assay for vaccine-matched influenza A and B	Influenza A included H1N1 and H3N2 and influenza B strains included Victoria-lineage. Seroconversion is defined as either a baseline HI titer <1:10 and a post-vaccination titer ≥1:40 or a baseline HI titer ≥1:10 and a minimum 4-fold rise in post-vaccination HI antibody titer.	28 days after vaccination
Incidence of adverse reactions within 28 days after vaccination	Incidence of adverse reactions within 28 days after vaccination. Adverse reactions include solicited and unsolicited adverse reactions. Solicited local (injection site) symptoms: pain, swelling, erythema, induration, pruritus; Solicited systemic (non-injection site) symptoms: fever (axillary temperature), fatigue, myalgia, headache, hypersensitivity reaction.	28 days after vaccination

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
The seroprotection rates (SPRs) of HI antibodies at day 28 ,as measured by HAI assay for vaccine-matched influenza A and B	Influenza A included H1N1 and H3N2 and influenza B strains included Victoria-lineage. Seroprotection is defined as an HI titer ≥1: 40.	28 days after vaccination
The geometric mean titers (GMTs) of HI antibodies at day 28 ,as measured by HAI assay for vaccine-matched influenza A and B	Influenza A included H1N1 and H3N2 and influenza B strains included Victoria-lineage. Log-transformed post-vaccination HI antibody titer will be the dependent variable, with treatment group as fixed effect and log-transformed pre-vaccination HI antibody titer as covariate. Least-squares mean differences with two-sided 95% CIs will be estimated and back-transformed via exponentiation to derive adjusted GMT ratios (experimental vs control) and corresponding two-sided 95% CIs.	28 days after vaccination
The geometric mean fold rises (GMFRs) of HI antibodies at day 28 ,as measured by HAI assay for vaccine-matched influenza A and B	Influenza A included H1N1 and H3N2 and influenza B strains included Victoria-lineage. Geometric mean of antibody fold-rise with two-sided 95% CI will be calculated , along with the geometric mean ratio and its corresponding two-sided 95% CI.	28 days after vaccination
The SCRs of HI antibodies at delivery, as measured by HAI assay for vaccine-matched influenza A and B	Influenza A included H1N1 and H3N2 and influenza B strains included Victoria-lineage. Seroconversion is defined as either a baseline HI titer <1:10 and a post-vaccination titer ≥1:40 or a baseline HI titer ≥1:10 and a minimum 4-fold rise in post-vaccination HI antibody titer.	At the date of delivery , estimated to be 6-18 weeks after randomization.
The SPRs of HI antibodies at delivery ,as measured by HAI assay for vaccine-matched influenza A and B	Influenza A included H1N1 and H3N2 and influenza B strains included Victoria-lineage. Seroprotection is defined as an HI titer ≥1: 40.	At the date of delivery , estimated to be 6-18 weeks after randomization.
The GMTs of HI antibodies at delivery,as measured by HAI assay for vaccine-matched influenza A and B	Influenza A included H1N1 and H3N2 and influenza B strains included Victoria-lineage. Log-transformed post-vaccination HI antibody titer will be the dependent variable, with treatment group as fixed effect and log-transformed pre-vaccination HI antibody titer as covariate. Least-squares mean differences with two-sided 95% CIs will be estimated and back-transformed via exponentiation to derive adjusted GMT ratios (experimental vs control) and corresponding two-sided 95% CIs.	At the date of delivery , estimated to be 6-18 weeks after randomization.
The GMFRs of HI antibodies at delivery,as measured by HAI assay for vaccine-matched influenza A and B	Influenza A included H1N1 and H3N2 and influenza B strains included Victoria-lineage. Geometric mean of antibody fold-rise with two-sided 95% CI will be calculated , along with the geometric mean ratio and its corresponding two-sided 95% CI.	At the date of delivery , estimated to be 6-18 weeks after randomization.
The SPRs of HI antibodies in cord blood at delivery ,as measured by HAI assay for vaccine-matched influenza A and B	Influenza A included H1N1 and H3N2 and influenza B strains included Victoria-lineage. Seroprotection is defined as an HI titer ≥1: 40.	At the date of delivery, estimated to be 6-18 weeks after randomization
The GMTs of HI antibodies in cord blood at delivery, as measured by HAI assay for vaccine-matched influenza A and B	Influenza A included H1N1 and H3N2 and influenza B strains included Victoria-lineage. Log-transformed post-vaccination HI antibody titer will be the dependent variable, with treatment group as fixed effect and log-transformed pre-vaccination HI antibody titer as covariate. Least-squares mean differences with two-sided 95% CIs will be estimated and back-transformed via exponentiation to derive adjusted GMT ratios (experimental vs control) and corresponding two-sided 95% CIs.	At the date of delivery, estimated to be 6-18 weeks after randomization
Incidence of serious adverse events from vaccination through 3 months after delivery.	Serious adverse events within 3 months after delivery.	From vaccination to 3 months after delivery.
Pregnancy outcomes	Pregnancy outcomes: term birth, preterm birth, elective termination of pregnancy, fetal death, and gestational complications, etc.	At the date of delivery, estimated to be 6-18 weeks after randomization
Neonatal birth outcomes	Birth outcomes: normal status, low birth weight, congenital malformations, neonatal NICU admission, and neonatal death, etc.	3 months after delivery

Collaborators and Investigators

• Sponsor: Sinovac Biotech Co., Ltd
• Investigators: Principal Investigator: Qi Hongbo, First Affiliated Hospital of Chongqing Medical University

Study record dates

Study Major Dates

• Study Start (Estimated): October 1, 2026
• Primary Completion (Estimated): February 1, 2027
• Study Completion (Estimated): April 1, 2027

Study Registration Dates

• First Submitted: August 28, 2026
• First Submitted That Met QC Criteria: September 16, 2026
• First Posted (Actual): September 21, 2026

Study Record Updates

• Last Update Posted (Actual): September 21, 2026
• Last Update Submitted That Met QC Criteria: September 16, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: pregnant women
• Additional Relevant MeSH Terms: Respiratory Tract Infections; Infections; Orthomyxoviridae Infections; RNA Virus Infections; Virus Diseases; Respiratory Tract Diseases; Influenza, Human; vaxigrip
• Other Study ID Numbers: PRO-INF-4015

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No