A Phase IV Study to Evaluate the Immune Responses of Subunit Influenza Vaccine in Healthy Adults

NCT07854392 | Recruiting Phase 4

• 1 other identifier: K-2026-070-01
• Study Type: interventional
• Target: 138
• Locations: 1 country
• Sites: 1

Brief Summary

This is a prospective, open-label, parallel time-cohort study designed to characterize the humoral and cellular immune responses induced by a subunit influenza vaccine (manufactured by Ab\&B Bio-tech Co., Ltd.JS) in healthy adults within one month after vaccination. Eligible participants will receive a single intramuscular dose and will be assigned in parallel to one of two blood-sampling schedules to capture the kinetic profile of the immune response: Group A (pre-vaccination, Day 5, and Day 14 post-vaccination) and Group B (pre-vaccination, Day 7, and Day 21 post-vaccination). Hemagglutination inhibition (HI) antibody titers will be measured to assess humoral immunity, while circulating CD4⁺ and CD8⁺ T-cell levels will be analyzed to evaluate cellular immunity. The occurrence of adverse events（AEs) and serious adverse events(SAEs) within 28 days post-vaccination will be recorded.

Conditions

Influenza

Keywords

Influenza, Human; Immune Response; Safety; Healthy Adults; Subunit Influenza Vaccine

Outcome Measures

Primary Outcomes (4)

• GMTs of HI antibodies against the three vaccine strains (Group B, Day 21 post-vaccination)

  Influenza A includes H1N1 and H3N2; influenza B includes Victoria-lineage. Geometric mean HI antibody titer for each strain will be calculated with two-sided 95% CIs.

  Day 21 post-vaccination (Group B)

• GMIs of HI antibodies against the three vaccine strains (Group B, Day 21 post-vaccination)

  Geometric mean fold increase in HI antibody titer from pre-vaccination (Day 0) to Day 21 for each strain, with two-sided 95% CIs.

  Day 21 post-vaccination (Group B)

• SCRs of HI antibodies against the three vaccine strains (Group B, Day 21 post-vaccination)

  Seroconversion is defined as either a pre-vaccination HI titer \<1:10 with a post-vaccination titer ≥1:40, or a pre-vaccination HI titer ≥1:10 with at least a four-fold increase in titer.

  Day 21 post-vaccination (Group B)

• SPRs of HI antibodies against the three vaccine strains (Group B, Day 21 post-vaccination)

  Seroprotection is defined as an HI titer ≥1:40.

  Day 21 post-vaccination (Group B)

Secondary Outcomes (7)

• GMTs of HI antibodies against the three vaccine strains (Group A, Day 5 and Day 14 post-vaccination)

  Day 5 and Day 14 post-vaccination (Group A)

• GMTs of HI antibodies against the three vaccine strains (Group B, Day 7 post-vaccination)

  Day 7 post-vaccination (Group B)

• Antigen-specific CD4⁺ T-cell counts and proportions (Group A: Day 0, Day 5, Day 14; Group B: Day 0, Day 7, Day 21)

  Day 0, Day 5, Day 14 (Group A); Day 0, Day 7, Day 21(Group B:)

• Antigen-specific CD8⁺ T-cell counts and proportions (Group A: Day 0, Day 5, Day 14; Group B: Day 0, Day 7, Day 21)

  Day 0, Day 5, Day 14 (Group A); Day 0, Day 7, Day 21(Group B)

• CD4⁺/CD8⁺ T-cell ratio (Group A: Day 0, Day 5, Day 14; Group B: Day 0, Day 7, Day 21)

  Day 0, Day 5, Day 14 (Group A); Day 0, Day 7, Day 21(Group B)

Study Arms (2)

Group A

EXPERIMENTAL

Biological: Group A

Group B

EXPERIMENTAL

Biological: Group B

Interventions

Group A BIOLOGICAL

Participants will receive one dose of Subunit Influenza Vaccine

Group A

Group B BIOLOGICAL

Participants will receive one dose of Subunit Influenza Vaccine

Group B

Eligibility Criteria

• Age: 18 Years - 59 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Adults aged between 18 and 59 years at the time of informed consent signature.
• Judged by the investigator to be in good health, based on medical history and physical examination findings obtained at screening.
• Able to comprehend and voluntarily provide written informed consent, and willing to comply with all study procedures and requirements.

You may not qualify if:

• Known allergy to any component of the vaccine, including excipients, formaldehyde, or Triton N-101.
• Confirmed influenza infection or influenza-like illness within the past 6 months, or close contact with a confirmed influenza case within 14 days prior to the screening visit.
• Receipt of any influenza vaccine (licensed or investigational) within the past 6 months.
• Receipt of any licensed vaccine within 28 days prior to study vaccination, or planned receipt of any licensed vaccine within 28 days after study vaccination.
• Receipt of blood products or immunoglobulin within the past 3 months, or planned receipt within 1 month after study vaccination.
• Female participants who are known to be pregnant or breastfeeding; female participants of childbearing potential with a positive pregnancy test at screening; or those planning pregnancy within the next 3 months.
• Presence of acute illness, acute exacerbation of a chronic disease, or fever (axillary temperature ≥37.3 °C) within 3 days prior to vaccination. Use of anti-inflammatory, antibiotic, anti-allergic, or antiviral medications within 3 days prior to vaccination due to illness, including but not limited to acetaminophen, ibuprofen, loratadine, penicillins, cephalosporins, ribavirin, oseltamivir, and acyclovir.
• Systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg on the day of vaccination.
• Severe chronic cardiovascular or pulmonary disease:
• Heart failure with a history of acute exacerbation within the past 2 years;
• Chronic obstructive pulmonary disease (COPD) with a history of acute exacerbation within the past 2 years;
• Chronic interstitial lung disease with acute exacerbation or requirement for treatment adjustment within the past 2 years;
• \- History of asthma exacerbation within the past 2 years, or worsening asthma symptoms requiring adjustment of controller medication within the past 2 months;
• Uncontrolled serious arrhythmia, or hospitalization for acute arrhythmia or regular antiarrhythmic medication within the past 6 months;
• Unstable coronary artery disease within the past 3 months, as evidenced by percutaneous coronary intervention (e.g., stent implantation), coronary artery bypass grafting (CABG), newly initiated cardiac medication for symptom control, or unstable angina.

Sponsors & Collaborators

• Ab&B Bio-tech Co., Ltd.JS: lead
• Zhejiang Provincial Center for Disease Control and Prevention: collaborator
• Shangyu District Center for Disease Control and Prevention: collaborator

Study Sites (1)

Shangyu District Center for Disease Control and Prevention

Shaoxing, Zhejiang, 312000, China

RECRUITING

MeSH Terms

Conditions

Influenza, Human

Condition Hierarchy (Ancestors)

Respiratory Tract Infections; Infections; Orthomyxoviridae Infections; RNA Virus Infections; Virus Diseases; Respiratory Tract Diseases

Central Study Contacts

Hui Liang

CONTACT

86-18257111511; hliang@cdc.zj.cn

Study Design

• Study Type: interventional
• Phase: phase 4
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: PREVENTION
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: September 27, 2026
• First Posted: October 2, 2026
• Study Start (Estimated): October 11, 2026
• Primary Completion (Estimated): November 30, 2026
• Study Completion (Estimated): October 11, 2027
• Last Updated: October 2, 2026

Record last verified: 2026-09

Locations

CN (1)