Trial Outcomes & Findings for Recombinant Influenza Vaccine Versus Standard Egg-Based Inactivated Influenza Vaccine in Adults 18-64 Years (NCT NCT05514002)
NCT ID: NCT05514002
Last Updated: 2026-07-30
Results Overview
Number of participants with RT-PCR-confirmed influenza infection during the influenza circulation period. Relative vaccine effectiveness (rVE) was calculated as (1 - hazard ratio comparing RIV vs SD-IIV) × 100%.
COMPLETED
PHASE4
3988 participants
From ≥14 days after vaccination through end of surveillance (up to 16 weeks)
2026-07-30
Participant Flow
A randomized, participant- and investigator-blinded, active-comparator trial conducted during the 2022-2023 Northern Hemisphere influenza season at 7 geographic sites in the United States. Participants were randomized 1:1 to receive recombinant influenza vaccine (RIV) or standard-dose inactivated influenza vaccine (SD IIV).
Participant milestones
| Measure |
Quadrivalent Recombinant Influenza Vaccine (RIV4)
Participants received a single 0.5 mL intramuscular dose of quadrivalent recombinant influenza vaccine (Flublok Quadrivalent, Sanofi Pasteur) during the 2022-2023 influenza season.
|
Quadrivalent Standard-Dose Egg-Based Inactivated Influenza Vaccine (SD-IIV4)
Participants received a single 0.5 mL intramuscular dose of quadrivalent standard-dose egg-based inactivated influenza vaccine (Fluzone Quadrivalent, Sanofi Pasteur) during the 2022-2023 influenza season.
|
|---|---|---|
|
Overall Study
STARTED
|
1995
|
1993
|
|
Overall Study
COMPLETED
|
1976
|
1976
|
|
Overall Study
NOT COMPLETED
|
19
|
17
|
Reasons for withdrawal
| Measure |
Quadrivalent Recombinant Influenza Vaccine (RIV4)
Participants received a single 0.5 mL intramuscular dose of quadrivalent recombinant influenza vaccine (Flublok Quadrivalent, Sanofi Pasteur) during the 2022-2023 influenza season.
|
Quadrivalent Standard-Dose Egg-Based Inactivated Influenza Vaccine (SD-IIV4)
Participants received a single 0.5 mL intramuscular dose of quadrivalent standard-dose egg-based inactivated influenza vaccine (Fluzone Quadrivalent, Sanofi Pasteur) during the 2022-2023 influenza season.
|
|---|---|---|
|
Overall Study
Lost to Follow-up
|
19
|
17
|
Baseline Characteristics
Participants in the modified intention-to-treat population with non-missing age data. Age categories sum to the overall number analyzed for each arm.
Baseline characteristics by cohort
| Measure |
Quadrivalent Recombinant Influenza Vaccine (RIV4)
n=1976 Participants
Participants received a single 0.5 mL intramuscular dose of quadrivalent recombinant influenza vaccine (Flublok Quadrivalent, Sanofi Pasteur) during the 2022-2023 influenza season.
|
Quadrivalent Standard-Dose Egg-Based Inactivated Influenza Vaccine (SD-IIV4)
n=1976 Participants
Participants received a single 0.5 mL intramuscular dose of quadrivalent standard-dose egg-based inactivated influenza vaccine (Fluzone Quadrivalent, Sanofi Pasteur) during the 2022-2023 influenza season.
|
Total
n=3952 Participants
Total of all reporting groups
|
|---|---|---|---|
|
Age, Customized
18-49 years
|
1645 Participants
n=20 Participants • Participants in the modified intention-to-treat population with non-missing age data. Age categories sum to the overall number analyzed for each arm.
|
1646 Participants
n=20 Participants • Participants in the modified intention-to-treat population with non-missing age data. Age categories sum to the overall number analyzed for each arm.
|
3291 Participants
n=40 Participants • Participants in the modified intention-to-treat population with non-missing age data. Age categories sum to the overall number analyzed for each arm.
|
|
Age, Customized
50-64 years
|
331 Participants
n=20 Participants • Participants in the modified intention-to-treat population with non-missing age data. Age categories sum to the overall number analyzed for each arm.
|
330 Participants
n=20 Participants • Participants in the modified intention-to-treat population with non-missing age data. Age categories sum to the overall number analyzed for each arm.
|
661 Participants
n=40 Participants • Participants in the modified intention-to-treat population with non-missing age data. Age categories sum to the overall number analyzed for each arm.
|
|
Sex/Gender, Customized
Female
|
1255 Participants
n=20 Participants
|
1221 Participants
n=20 Participants
|
2476 Participants
n=40 Participants
|
|
Sex/Gender, Customized
Male
|
684 Participants
n=20 Participants
|
722 Participants
n=20 Participants
|
1406 Participants
n=40 Participants
|
|
Sex/Gender, Customized
Transgender/Other
|
12 Participants
n=20 Participants
|
12 Participants
n=20 Participants
|
24 Participants
n=40 Participants
|
|
Sex/Gender, Customized
None of these
|
25 Participants
n=20 Participants
|
21 Participants
n=20 Participants
|
46 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
American Indian or Alaska Native
|
14 Participants
n=20 Participants
|
15 Participants
n=20 Participants
|
29 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Asian
|
390 Participants
n=20 Participants
|
392 Participants
n=20 Participants
|
782 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Black or African American
|
232 Participants
n=20 Participants
|
228 Participants
n=20 Participants
|
460 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Native Hawaiian or Other Pacific Islander
|
1 Participants
n=20 Participants
|
3 Participants
n=20 Participants
|
4 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
White
|
1173 Participants
n=20 Participants
|
1175 Participants
n=20 Participants
|
2348 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Multiracial
|
73 Participants
n=20 Participants
|
75 Participants
n=20 Participants
|
148 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Declined/missing race
|
93 Participants
n=20 Participants
|
88 Participants
n=20 Participants
|
181 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Hispanic or Latino/a
|
301 Participants
n=20 Participants
|
299 Participants
n=20 Participants
|
600 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Not Hispanic or Latino/a
|
1633 Participants
n=20 Participants
|
1641 Participants
n=20 Participants
|
3274 Participants
n=40 Participants
|
|
Race/Ethnicity, Customized
Declined/missing ethnicity
|
42 Participants
n=20 Participants
|
36 Participants
n=20 Participants
|
78 Participants
n=40 Participants
|
|
Region of Enrollment
United States
|
1976 participants
n=20 Participants
|
1976 participants
n=20 Participants
|
3952 participants
n=40 Participants
|
PRIMARY outcome
Timeframe: From ≥14 days after vaccination through end of surveillance (up to 16 weeks)Population: Analytic modified intention-to-treat population. Participants were excluded if they tested influenza-positive within 14 days after vaccination or did not respond to surveillance contacts beyond 14 days after vaccination. The resulting analysis population included 1,963 participants in the recombinant influenza vaccine group and 1,964 participants in the standard-dose inactivated influenza vaccine group.
Number of participants with RT-PCR-confirmed influenza infection during the influenza circulation period. Relative vaccine effectiveness (rVE) was calculated as (1 - hazard ratio comparing RIV vs SD-IIV) × 100%.
Outcome measures
| Measure |
Quadrivalent Recombinant Influenza Vaccine (RIV4)
n=1963 Participants
Participants received a single 0.5 mL intramuscular dose of quadrivalent recombinant influenza vaccine (Flublok Quadrivalent, Sanofi Pasteur) during the 2022-2023 influenza season.
|
Quadrivalent Standard-Dose Egg-Based Inactivated Influenza Vaccine (SD-IIV4)
n=1964 Participants
Participants received a single 0.5 mL intramuscular dose of quadrivalent standard-dose egg-based inactivated influenza vaccine (Fluzone Quadrivalent, Sanofi Pasteur) during the 2022-2023 influenza season.
|
|---|---|---|
|
RT-PCR-Confirmed Influenza Infection
RT-PCR-confirmed influenza
|
20 participants
|
28 participants
|
|
RT-PCR-Confirmed Influenza Infection
No RT-PCR-confirmed influenza
|
1943 participants
|
1936 participants
|
SECONDARY outcome
Timeframe: Up to 14 days after onset of influenza illnessPopulation: Participants with RT-PCR-confirmed influenza illness who completed outcome assessments. Twenty participants in the recombinant influenza vaccine group and 25 participants in the standard-dose inactivated influenza vaccine group were included in this analysis.
Number of days from onset of influenza illness until return to usual health, defined as two consecutive days reporting return to usual health on the FLU-PRO Plus instrument.
Outcome measures
| Measure |
Quadrivalent Recombinant Influenza Vaccine (RIV4)
n=20 Participants
Participants received a single 0.5 mL intramuscular dose of quadrivalent recombinant influenza vaccine (Flublok Quadrivalent, Sanofi Pasteur) during the 2022-2023 influenza season.
|
Quadrivalent Standard-Dose Egg-Based Inactivated Influenza Vaccine (SD-IIV4)
n=25 Participants
Participants received a single 0.5 mL intramuscular dose of quadrivalent standard-dose egg-based inactivated influenza vaccine (Fluzone Quadrivalent, Sanofi Pasteur) during the 2022-2023 influenza season.
|
|---|---|---|
|
Time to Return to Usual Health Following Influenza Illness
|
10.5 days
Standard Deviation 3.3
|
10.9 days
Standard Deviation 2.7
|
Adverse Events
Quadrivalent Recombinant Influenza Vaccine (RIV4)
Quadrivalent Standard-Dose Egg-Based Inactivated Influenza Vaccine (SD-IIV4)
Serious adverse events
Adverse event data not reported
Other adverse events
Adverse event data not reported
Additional Information
Fatimah S. Dawood, MD
Centers for Disease Control and Prevention
Results disclosure agreements
- Principal investigator is a sponsor employee
- Publication restrictions are in place