A Phase 4 interventional study of Flucelvax® (ccIIV3) and Flublok® (RIV3) in Influenza, sponsored by Duke University. Completed at 7 sites in United States. Open to participants aged 18 Years to 64 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-07-28.
Sponsored by Duke University · Phase 4, Interventional, and Prevention
This study is a randomized immunogenicity study in an enrolled cohort with active surveillance for influenza-like illness (ILI). During this study, participants will be randomly assigned to receive an approved cell culture-based influenza vaccine (Flucelvax®) versus a licensed comparator influenza vaccine (Flublok®). Blood samples from participants will be collected for measurement of biomarkers of immune response at baseline (visit 1; day 1), post-vaccination (visit 2; day 29), and post-season (visit 3; day 181). Participants will be asked if they wish to also provide saliva specimens at baseline (visit 1; day 1), post-vaccination (visit 2; day 29), and post-season (visit 3; day 181). Serum and peripheral blood mononuclear cells (PBMC) and plasma samples will be isolated from whole blood and tested for biomarkers of vaccine immunogenicity, and duration of antibody responses.
Participants will receive electronic surveys via email or text message weekly asking about changes in health status and new ILI symptoms; those reporting illness may be asked to provide a respiratory swab for laboratory testing for influenza and other respiratory viruses and up to 2 additional blood draws (acute [\<10 days after symptom onset] and convalescent [28 days after acute visit if lab-confirmed positive for influenza]).
2,214 studies on the registry are indexed under Influenza, Human; 164 are open to participants now.
This study's enrollment of 606 is above the median of 238 across 1,853 interventional studies indexed under Influenza, Human.
Browse Influenza, Human studies →Duke University is the lead sponsor of 2,025 studies on the registry; 275 are open to participants now.
Of its 194 completed or terminated interventional studies of FDA-regulated products, 159 (82%) have results posted.
Counted across the registry records on this site, refreshed daily.
Exclusion Criteria:
Temporary Delay Criteria (Visit 1)
1. History of febrile illness (> 100.0°F or 37.8°C) within the past 72 hours prior to vaccine administration
Participants will receive Flucelvax® (ccIIV3) at Visit 1.
Biological: Flucelvax® (ccIIV3)
Participants will receive Flublok® (RIV3) at Visit 1.
Biological: Flublok® (RIV3)
Participants will receive Flucelvax® (ccIIV3)
Participants will receive Flublok® (RIV3)
Percent of Participants With a Seroprotective HAI Titer (≥1:40)
The percent of participants with a seroprotective antibody titer (≥1:40) for each influenza vaccine antigen was determined. Cell-grown A(H1N1)pdm09 and B/Victoria were measured by hemagglutination inhibition (HAI), while A(H3N2) titers were measured by microneutralization.
Time frame: Visit 2 (Days 28-42, Post-vaccination)
The Geometric Mean Titer (GMT) of HAI Antibody
The geometric mean antibody titer (GMT) for each influenza vaccine antigen in the 2024-2025 influenza season. GMTs were calculated as the anti-log of the mean of log-transformed titers. Cell-grown A(H1N1)pdm09 and B/Victoria were assessed by hemagglutination inhibition (HAI), whereas A(H3N2) was assessed by microneutralization.
Time frame: Up to Visit 2 (Days 28-42, Post-vaccination)
Percent of Participants Demonstrating Seroconversion From Baseline
The percent of participants in each vaccination group demonstrating seroconversion from Baseline at Day 29 (defined as a titer ≥1:40 at Day 29 if the baseline titer is \<1:10, or a ≥4-fold rise in titer at Day 29 if the baseline titer is ≥1:10) for each vaccine antigen. Viruses tested were cell-grown A(H1N1)pdm09 and B/Victoria using hemagglutination inhibition (HAI), and A(H3N2) using microneutralization.
Time frame: Day 29 post-vaccination assessment (Visit 2; scheduled for Day 29 with an allowable window of Days 28-42 post-vaccination)
Geometric Mean Fold Rise (GMFR) in HAI Titer From Baseline
The geometric mean fold rise (GMFR) in antibody titers from Baseline to Day 29 for each influenza vaccine antigen. Cell-grown A(H1N1)pdm09 and B/Victoria were assessed using hemagglutination inhibition (HAI), whereas A(H3N2) was assessed using microneutralization.
Time frame: Day 29 post-vaccination assessment (Visit 2; scheduled for Day 29 with an allowable window of Days 28-42 post-vaccination)
| Milestone | Flucelvax® (ccIIV3) | Flublok® (RIV3) |
|---|---|---|
| Started | 301 | 298 |
| Completed | 299 | 296 |
| Not completed | 2 | 2 |
| Withdrew: Protocol violation | 2 | 2 |
The percent of participants with a seroprotective antibody titer (≥1:40) for each influenza vaccine antigen was determined. Cell-grown A(H1N1)pdm09 and B/Victoria were measured by hemagglutination inhibition (HAI), while A(H3N2) titers were measured by microneutralization.
| percentage of participants | Flucelvax® (ccIIV3) | Flublok® (RIV3) |
|---|---|---|
| A(H1N1)pdm09 | 81.3 (70.7 to 88.7) | 88.2 (78.6 to 93.8) |
| A(H3N2) | 82.7 (72.2 to 89.7) | 94.7 (86.6 to 98.0) |
| B/Victoria | 74.7 (63.5 to 83.3) | 86.8 (77.1 to 92.8) |
The geometric mean antibody titer (GMT) for each influenza vaccine antigen in the 2024-2025 influenza season. GMTs were calculated as the anti-log of the mean of log-transformed titers. Cell-grown A(H1N1)pdm09 and B/Victoria were assessed by hemagglutination inhibition (HAI), whereas A(H3N2) was assessed by microneutralization.
| titers | Flucelvax® (ccIIV3) | Flublok® (RIV3) |
|---|---|---|
| A(H1N1)pdm09: Pre-vaccine | 31.0 (22.8 to 42.2) | 24.4 (17.8 to 33.6) |
| A(H1N1)pdm09: Post-vaccine | 101.2 (74.1 to 138.2) | 157.1 (116.1 to 212.6) |
| A(H3N2): Pre-vaccine | 28.6 (21.1 to 38.8) | 29.2 (21.3 to 40.1) |
| A(H3N2): Post-vaccine | 110.0 (82.8 to 148.8) | 349.7 (259.7 to 470.8) |
| B/Victoria: Pre-vaccine | 22.1 (17.1 to 28.7) | 29.1 (22.3 to 38.2) |
| B/Victoria: Post-vaccine | 73.9 (55.9 to 97.9) | 132.7 (99.7 to 176.5) |
The percent of participants in each vaccination group demonstrating seroconversion from Baseline at Day 29 (defined as a titer ≥1:40 at Day 29 if the baseline titer is \<1:10, or a ≥4-fold rise in titer at Day 29 if the baseline titer is ≥1:10) for each vaccine antigen. Viruses tested were cell-grown A(H1N1)pdm09 and B/Victoria using hemagglutination inhibition (HAI), and A(H3N2) using microneutralization.
| percentage of participants | Flucelvax® (ccIIV3) | Flublok® (RIV3) |
|---|---|---|
| A(H1N1)pdm09 | 30.7 (21.2 to 42.1) | 68.4 (57.0 to 78.0) |
| A(H3N2) | 45.3 (34.3 to 56.8) | 86.8 (77.1 to 92.8) |
| B/Victoria | 32.0 (22.3 to 43.5) | 48.7 (37.5 to 60.0) |
The geometric mean fold rise (GMFR) in antibody titers from Baseline to Day 29 for each influenza vaccine antigen. Cell-grown A(H1N1)pdm09 and B/Victoria were assessed using hemagglutination inhibition (HAI), whereas A(H3N2) was assessed using microneutralization.
| Fold Change | Flucelvax® (ccIIV3) | Flublok® (RIV3) |
|---|---|---|
| A(H1N1)pdm09 | 3.3 (2.5 to 4.3) | 6.4 (5.2 to 8.0) |
| A(H3N2) | 3.9 (3.0 to 5.0) | 12.0 (8.7 to 16.4) |
| B/Victoria | 3.3 (2.7 to 4.1) | 4.6 (3.5 to 6.0) |
Collected over Up to approximately 8 months. Non-serious events are listed at a 0% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Flucelvax® (ccIIV3) | 1/301 (0.3%) | 3/301 (1%) | — |
| Flublok® (RIV) | 0/298 (0%) | 0/298 (0%) | — |
| Event | Flucelvax® (ccIIV3) | Flublok® (RIV) |
|---|---|---|
| Small cell lung cancer stage IVNeoplasms benign, malignant and unspecified (incl cysts and polyps) | 1/301 | 0/298 |
| Kidney stonesRenal and urinary disorders | 1/301 | 0/298 |
| WhiplashInjury, poisoning and procedural complications | 1/301 | 0/298 |
Intention-to-treat population: Any participant who was enrolled and randomized.
| Age, Continuous(years) | Flucelvax® (ccIIV3) | Flublok (RIV3) | Total |
|---|---|---|---|
| Median | 37 (28 to 47) | 40 (29 to 52) | 38 (28 to 50) |
| Age, Customized(Participants) | Flucelvax® (ccIIV3) | Flublok (RIV3) | Total |
|---|---|---|---|
| 18-49 years | 234 | 211 | 445 |
| 50-64 years | 67 | 87 | 154 |
| Sex/Gender, Customized(Participants) | Flucelvax® (ccIIV3) | Flublok (RIV3) | Total |
|---|---|---|---|
| Female | 206 | 207 | 413 |
| Male | 95 | 88 | 183 |
| Unknown | 0 | 3 | 3 |
| Race/Ethnicity, Customized(Participants) | Flucelvax® (ccIIV3) | Flublok (RIV3) | Total |
|---|---|---|---|
| Hispanic | 40 | 34 | 74 |
| American Indian or Alaska Native | 2 | 0 | 2 |
| Asian | 41 | 37 | 78 |
| Black or African American | 18 | 18 | 36 |
| Middle Eastern or North African | 3 | 0 | 3 |
| Multiple Races | 5 | 9 | 14 |
| Native Hawaiian or Other Pacific Islander | 0 | 0 | 0 |
| White | 190 | 196 | 386 |
| Other | 1 | 2 | 3 |
| Unknown | 1 | 2 | 3 |
| Enrollment Site(Participants) | Flucelvax® (ccIIV3) | Flublok (RIV3) | Total |
|---|---|---|---|
| Arizona State | 69 | 69 | 138 |
| Valleywise | 23 | 22 | 45 |
| Washington University | 75 | 75 | 150 |
| UH Hospital | 72 | 70 | 142 |
| Cleveland VA | 12 | 13 | 25 |
| University of Pittsburgh | 50 | 49 | 99 |
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