Trial Outcomes & Findings for Immunogenicity of Influenza Vaccinations (NCT NCT06518577)
NCT ID: NCT06518577
Last Updated: 2026-07-28
Results Overview
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.
COMPLETED
PHASE4
606 participants
Visit 2 (Days 28-42, Post-vaccination)
2026-07-28
Participant Flow
7 participants were not randomized to a vaccine group; 2 due to protocol violations and 5 were considered screen fails.
Participant milestones
| Measure |
Flublok® (RIV3)
Participants will receive Flublok® (RIV3) at Visit 1.
Flublok® (RIV3): Participants will receive Flublok® (RIV3)
|
Flucelvax® (ccIIV3)
Participants will receive Flucelvax® (ccIIV3) at Visit 1.
Flucelvax® (ccIIV3): Participants will receive Flucelvax® (ccIIV3)
|
|---|---|---|
|
Overall Study
STARTED
|
298
|
301
|
|
Overall Study
COMPLETED
|
296
|
299
|
|
Overall Study
NOT COMPLETED
|
2
|
2
|
Reasons for withdrawal
| Measure |
Flublok® (RIV3)
Participants will receive Flublok® (RIV3) at Visit 1.
Flublok® (RIV3): Participants will receive Flublok® (RIV3)
|
Flucelvax® (ccIIV3)
Participants will receive Flucelvax® (ccIIV3) at Visit 1.
Flucelvax® (ccIIV3): Participants will receive Flucelvax® (ccIIV3)
|
|---|---|---|
|
Overall Study
Protocol Violation
|
2
|
2
|
Baseline Characteristics
Immunogenicity of Influenza Vaccinations
Baseline characteristics by cohort
| Measure |
Flucelvax® (ccIIV3)
n=301 Participants
Participants will receive Flucelvax® (ccIIV3) at Visit 1.
Flucelvax® (ccIIV3): Participants will receive Flucelvax® (ccIIV3)
|
Flublok (RIV3)
n=298 Participants
Participants will receive Flublok® (RIV3) at Visit 1.
Flublok® (RIV3): Participants will receive Flublok® (RIV3)
|
Total
n=599 Participants
Total of all reporting groups
|
|---|---|---|---|
|
Age, Continuous
|
37 years
n=20 Participants
|
40 years
n=20 Participants
|
38 years
n=40 Participants
|
|
Age, Customized
18-49 years
|
234 Participants
n=20 Participants
|
211 Participants
n=20 Participants
|
445 Participants
n=40 Participants
|
|
Age, Customized
50-64 years
|
67 Participants
n=20 Participants
|
87 Participants
n=20 Participants
|
154 Participants
n=40 Participants
|
|
Sex/Gender, Customized
Female
|
206 Participants
n=20 Participants
|
207 Participants
n=20 Participants
|
413 Participants
n=40 Participants
|
|
Sex/Gender, Customized
Male
|
95 Participants
n=20 Participants
|
88 Participants
n=20 Participants
|
183 Participants
n=40 Participants
|
|
Sex/Gender, Customized
Unknown
|
0 Participants
n=20 Participants
|
3 Participants
n=20 Participants
|
3 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Hispanic
|
40 Participants
n=20 Participants
|
34 Participants
n=20 Participants
|
74 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
American Indian or Alaska Native
|
2 Participants
n=20 Participants
|
0 Participants
n=20 Participants
|
2 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Asian
|
41 Participants
n=20 Participants
|
37 Participants
n=20 Participants
|
78 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Black or African American
|
18 Participants
n=20 Participants
|
18 Participants
n=20 Participants
|
36 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Middle Eastern or North African
|
3 Participants
n=20 Participants
|
0 Participants
n=20 Participants
|
3 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Multiple Races
|
5 Participants
n=20 Participants
|
9 Participants
n=20 Participants
|
14 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Native Hawaiian or Other Pacific Islander
|
0 Participants
n=20 Participants
|
0 Participants
n=20 Participants
|
0 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
White
|
190 Participants
n=20 Participants
|
196 Participants
n=20 Participants
|
386 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Other
|
1 Participants
n=20 Participants
|
2 Participants
n=20 Participants
|
3 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Unknown
|
1 Participants
n=20 Participants
|
2 Participants
n=20 Participants
|
3 Participants
n=40 Participants
|
|
Enrollment Site
Arizona State
|
69 Participants
n=20 Participants
|
69 Participants
n=20 Participants
|
138 Participants
n=40 Participants
|
|
Enrollment Site
Valleywise
|
23 Participants
n=20 Participants
|
22 Participants
n=20 Participants
|
45 Participants
n=40 Participants
|
|
Enrollment Site
Washington University
|
75 Participants
n=20 Participants
|
75 Participants
n=20 Participants
|
150 Participants
n=40 Participants
|
|
Enrollment Site
UH Hospital
|
72 Participants
n=20 Participants
|
70 Participants
n=20 Participants
|
142 Participants
n=40 Participants
|
|
Enrollment Site
Cleveland VA
|
12 Participants
n=20 Participants
|
13 Participants
n=20 Participants
|
25 Participants
n=40 Participants
|
|
Enrollment Site
University of Pittsburgh
|
50 Participants
n=20 Participants
|
49 Participants
n=20 Participants
|
99 Participants
n=40 Participants
|
PRIMARY outcome
Timeframe: Visit 2 (Days 28-42, Post-vaccination)Population: Immunogenicity Population: A subset of the mITT population that includes only participants who received the study vaccine, provided Visit 1 and Visit 2 blood draws available with HAI titer results for analysis within the protocol-defined time frame, did not have an influenza infection between Visits 1 and 2, and had no protocol violations affecting immunogenicity.
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.
Outcome measures
| Measure |
Flucelvax® (ccIIV3)
n=75 Participants
Participants will receive Flucelvax® (ccIIV3) at Visit 1.
Flucelvax® (ccIIV3): Participants will receive Flucelvax® (ccIIV3)
|
Flublok® (RIV3)
n=76 Participants
Participants will receive Flublok® (RIV3) at Visit 1.
Flublok® (RIV3): Participants will receive Flublok® (RIV3)
|
|---|---|---|
|
Percent of Participants With a Seroprotective HAI Titer (≥1:40)
A(H1N1)pdm09
|
81.3 percentage of participants
Interval 70.7 to 88.7
|
88.2 percentage of participants
Interval 78.6 to 93.8
|
|
Percent of Participants With a Seroprotective HAI Titer (≥1:40)
A(H3N2)
|
82.7 percentage of participants
Interval 72.2 to 89.7
|
94.7 percentage of participants
Interval 86.6 to 98.0
|
|
Percent of Participants With a Seroprotective HAI Titer (≥1:40)
B/Victoria
|
74.7 percentage of participants
Interval 63.5 to 83.3
|
86.8 percentage of participants
Interval 77.1 to 92.8
|
PRIMARY outcome
Timeframe: Up to Visit 2 (Days 28-42, Post-vaccination)Population: Immunogenicity Population: A subset of the mITT population that includes only participants who received the study vaccine, provided Visit 1 and Visit 2 blood draws available with HAI titer results for analysis within the protocol-defined time frame, did not have an influenza infection between Visits 1 and 2, and had no protocol violations affecting immunogenicity.
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.
Outcome measures
| Measure |
Flucelvax® (ccIIV3)
n=75 Participants
Participants will receive Flucelvax® (ccIIV3) at Visit 1.
Flucelvax® (ccIIV3): Participants will receive Flucelvax® (ccIIV3)
|
Flublok® (RIV3)
n=76 Participants
Participants will receive Flublok® (RIV3) at Visit 1.
Flublok® (RIV3): Participants will receive Flublok® (RIV3)
|
|---|---|---|
|
The Geometric Mean Titer (GMT) of HAI Antibody
A(H1N1)pdm09: Pre-vaccine
|
31.0 titers
Interval 22.8 to 42.2
|
24.4 titers
Interval 17.8 to 33.6
|
|
The Geometric Mean Titer (GMT) of HAI Antibody
A(H1N1)pdm09: Post-vaccine
|
101.2 titers
Interval 74.1 to 138.2
|
157.1 titers
Interval 116.1 to 212.6
|
|
The Geometric Mean Titer (GMT) of HAI Antibody
A(H3N2): Pre-vaccine
|
28.6 titers
Interval 21.1 to 38.8
|
29.2 titers
Interval 21.3 to 40.1
|
|
The Geometric Mean Titer (GMT) of HAI Antibody
A(H3N2): Post-vaccine
|
110.0 titers
Interval 82.8 to 148.8
|
349.7 titers
Interval 259.7 to 470.8
|
|
The Geometric Mean Titer (GMT) of HAI Antibody
B/Victoria: Pre-vaccine
|
22.1 titers
Interval 17.1 to 28.7
|
29.1 titers
Interval 22.3 to 38.2
|
|
The Geometric Mean Titer (GMT) of HAI Antibody
B/Victoria: Post-vaccine
|
73.9 titers
Interval 55.9 to 97.9
|
132.7 titers
Interval 99.7 to 176.5
|
PRIMARY outcome
Timeframe: Day 29 post-vaccination assessment (Visit 2; scheduled for Day 29 with an allowable window of Days 28-42 post-vaccination)Population: Immunogenicity Population: A subset of the mITT population that includes only participants who received the study vaccine, provided Visit 1 and Visit 2 blood draws available with HAI titer results for analysis within the protocol-defined time frame, did not have an influenza infection between Visits 1 and 2, and had no protocol violations affecting immunogenicity.
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.
Outcome measures
| Measure |
Flucelvax® (ccIIV3)
n=75 Participants
Participants will receive Flucelvax® (ccIIV3) at Visit 1.
Flucelvax® (ccIIV3): Participants will receive Flucelvax® (ccIIV3)
|
Flublok® (RIV3)
n=76 Participants
Participants will receive Flublok® (RIV3) at Visit 1.
Flublok® (RIV3): Participants will receive Flublok® (RIV3)
|
|---|---|---|
|
Percent of Participants Demonstrating Seroconversion From Baseline
A(H1N1)pdm09
|
30.7 percentage of participants
Interval 21.2 to 42.1
|
68.4 percentage of participants
Interval 57.0 to 78.0
|
|
Percent of Participants Demonstrating Seroconversion From Baseline
A(H3N2)
|
45.3 percentage of participants
Interval 34.3 to 56.8
|
86.8 percentage of participants
Interval 77.1 to 92.8
|
|
Percent of Participants Demonstrating Seroconversion From Baseline
B/Victoria
|
32.0 percentage of participants
Interval 22.3 to 43.5
|
48.7 percentage of participants
Interval 37.5 to 60.0
|
PRIMARY outcome
Timeframe: Day 29 post-vaccination assessment (Visit 2; scheduled for Day 29 with an allowable window of Days 28-42 post-vaccination)Population: Immunogenicity Population: A subset of the mITT population that includes only participants who received the study vaccine, provided Visit 1 and Visit 2 blood draws available with HAI titer results for analysis within the protocol-defined time frame, did not have an influenza infection between Visits 1 and 2, and had no protocol violations affecting immunogenicity.
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.
Outcome measures
| Measure |
Flucelvax® (ccIIV3)
n=75 Participants
Participants will receive Flucelvax® (ccIIV3) at Visit 1.
Flucelvax® (ccIIV3): Participants will receive Flucelvax® (ccIIV3)
|
Flublok® (RIV3)
n=76 Participants
Participants will receive Flublok® (RIV3) at Visit 1.
Flublok® (RIV3): Participants will receive Flublok® (RIV3)
|
|---|---|---|
|
Geometric Mean Fold Rise (GMFR) in HAI Titer From Baseline
B/Victoria
|
3.3 Fold Change
Interval 2.7 to 4.1
|
4.6 Fold Change
Interval 3.5 to 6.0
|
|
Geometric Mean Fold Rise (GMFR) in HAI Titer From Baseline
A(H1N1)pdm09
|
3.3 Fold Change
Interval 2.5 to 4.3
|
6.4 Fold Change
Interval 5.2 to 8.0
|
|
Geometric Mean Fold Rise (GMFR) in HAI Titer From Baseline
A(H3N2)
|
3.9 Fold Change
Interval 3.0 to 5.0
|
12.0 Fold Change
Interval 8.7 to 16.4
|
Adverse Events
Flublok® (RIV)
Flucelvax® (ccIIV3)
Serious adverse events
| Measure |
Flublok® (RIV)
n=298 participants at risk
Participants will receive Flublok® (RIV) at Visit 1.
Flublok® (RIV): Participants will receive Flublok® (RIV)
|
Flucelvax® (ccIIV3)
n=301 participants at risk
Participants will receive Flucelvax® (ccIIV3) at Visit 1.
Flucelvax® (ccIIV3): Participants will receive Flucelvax® (ccIIV3)
|
|---|---|---|
|
Renal and urinary disorders
Kidney stones
|
0.00%
0/298 • Up to approximately 8 months
Serious adverse events (SAEs) were collected on each participant through study completion (up to approximately 8 months). Non-serious adverse events were not collected. The one reported mortality was determined not to be related to study procedures.
|
0.33%
1/301 • Number of events 1 • Up to approximately 8 months
Serious adverse events (SAEs) were collected on each participant through study completion (up to approximately 8 months). Non-serious adverse events were not collected. The one reported mortality was determined not to be related to study procedures.
|
|
Neoplasms benign, malignant and unspecified (incl cysts and polyps)
Small cell lung cancer stage IV
|
0.00%
0/298 • Up to approximately 8 months
Serious adverse events (SAEs) were collected on each participant through study completion (up to approximately 8 months). Non-serious adverse events were not collected. The one reported mortality was determined not to be related to study procedures.
|
0.33%
1/301 • Number of events 1 • Up to approximately 8 months
Serious adverse events (SAEs) were collected on each participant through study completion (up to approximately 8 months). Non-serious adverse events were not collected. The one reported mortality was determined not to be related to study procedures.
|
|
Injury, poisoning and procedural complications
Whiplash
|
0.00%
0/298 • Up to approximately 8 months
Serious adverse events (SAEs) were collected on each participant through study completion (up to approximately 8 months). Non-serious adverse events were not collected. The one reported mortality was determined not to be related to study procedures.
|
0.33%
1/301 • Number of events 1 • Up to approximately 8 months
Serious adverse events (SAEs) were collected on each participant through study completion (up to approximately 8 months). Non-serious adverse events were not collected. The one reported mortality was determined not to be related to study procedures.
|
Other adverse events
Adverse event data not reported
Additional Information
Results disclosure agreements
- Principal investigator is a sponsor employee
- Publication restrictions are in place