A Phase 2 interventional study of aH5N6c on Day 1 and aH5N6c on Day 22 in Influenza, Human, Influenza in Birds and Respiratory Tract Infections, sponsored by Seqirus. Completed at 18 sites in United States. Open to participants aged 18 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-05-13.
Sponsored by Seqirus (part of CSL Limited) · Phase 2, Interventional, and Prevention
This is a Phase 2, randomized, multi-center study in approximately 300 adults who received 2 doses of aH5N1c or placebo in and completed the parent study V89_18 in the \<65 years of age cohort. The study investigates whether two priming doses of MF59-adjuvanted H5N1 cell culture-derived vaccine (aH5N1c) followed by one or two booster vaccinations with a MF59-adjuvanted H5N6 cell culture derived vaccine (aH5N6c) 3 weeks apart elicit immune responses to the antigens used for priming (H5N1) and boosting (H5N6) after first and second heterologous booster vaccination.
Eligible subjects, who received 2 doses of aH5N1c in the parent study V89_18 are randomized in a 1:1 ratio to receive either two aH5N6c vaccinations, 3 weeks apart (group 1) or an aH5N6c vaccination on Day 1 and saline placebo on Day 22 (group 2). Eligible subjects, who received placebo in the parent study will receive two aH5N6c vaccinations, 3 weeks apart (group 3). After the second vaccine administration, subjects are monitored for approximately 6 months for safety and antibody persistence. The total study duration will be approximately 7 months per subject.
2,356 studies on the registry are indexed under Influenza, Human; 184 are open to participants now.
This study's enrollment of 260 is above the median of 227 across 1,957 interventional studies indexed under Influenza, Human.
Browse Influenza, Human studies →Seqirus is the lead sponsor of 53 studies on the registry; none are open to participants now.
Of its 15 completed or terminated interventional studies of FDA-regulated products, 10 (67%) have results posted.
First submitted after Seqirus became part of CSL Limited.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Vaccines made with a weakened form of the germ, such as measles–mumps–rubella (MMR), chickenpox and yellow fever. They can be risky when the immune system is weakened. Flu injections are not live; the nasal flu spray is.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Live vaccines
Vaccines made with a weakened form of the germ, such as measles–mumps–rubella (MMR), chickenpox and yellow fever. They can be risky when the immune system is weakened. Flu injections are not live; the nasal flu spray is.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Eligible subjects who received 2 doses of aH5N1c in the parent study V89\_18 and have been randomized to receive two aH5N6c vaccinations, 3 weeks apart
Biological: aH5N6c on Day 1 · Biological: aH5N6c on Day 22
Eligible subjects who received 2 doses of aH5N1c in the parent study V89\_18 and have been randomized to receive an aH5N6c vaccination on Day 1 and saline placebo on Day 22
Biological: aH5N6c on Day 1 · Biological: Placebo on Day 22
Eligible subjects who received placebo in the parent study V89\_18 receive two aH5N6c vaccinations, 3 weeks apart.
Biological: aH5N6c on Day 1 · Biological: aH5N6c on Day 22
MF59-adjuvanted cell-culture derived subunit inactivated monovalent A/H5N6 vaccine (aH5N6c) for intramuscular (IM) administration, containing 7.5 μg H5N6 hemagglutinin (HA) (A/Guangdong/18SF020/2018 (H5N6)-like) + 0.25 mL MF59 (approximately 0.5 mL total volume)
MF59-adjuvanted cell-culture derived subunit inactivated monovalent A/H5N6 vaccine (aH5N6c) for intramuscular (IM) administration, containing 7.5 μg H5N6 HA (A/Guangdong/18SF020/2018 (H5N6)-like) + 0.25 mL MF59 (approximately 0.5 mL total volume) given 3 weeks after the first aH5N6c vaccination
Saline placebo (sterile, 0.5 mL) given 3 weeks after the aH5N6c vaccination
Geometric Mean Titer (GMT) of Hemagglutination Inhibition (HI) Antibodies Against the H5N6 Strain
GMT pre-vaccination, 1 and 3 weeks post-vaccination 1, and 3 weeks post-vaccination 2 Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the per-protocol set (PPS); definitions are provided in the Statistical Analysis Plan (SAP). The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
Time frame: Day 1, Day 8, Day 22, Day 43
Geometric Mean Fold Increase (GMFI) of HI Antibodies Against the H5N6 Strain
GMFI 1 and 3 weeks post-vaccination 1, and 3 weeks post-vaccination 2 compared to pre-vaccination (Day 1) Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the PPS; definitions are provided in the SAP. The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
Time frame: Day 1, Day 8, Day 22, Day 43
Percentage of Subjects With HI Titers ≥1:40 Against the H5N6 Strain
Pre-vaccination, 1 and 3 weeks post-vaccination 1, and 3 weeks post-vaccination 2 Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the PPS; definitions are provided in the SAP. The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
Time frame: Day 1, Day 8, Day 22, Day 43
Percentage of Subjects With Seroconversion Against the H5N6 Strain
Seroconversion 1 and 3 weeks post-vaccination 1, and 3 weeks post-vaccination 2, defined as a ≥4-fold increase in HI titer post-vaccination in those with pre-vaccination titer ≥1:10, or a post-vaccination HI titer ≥1:40 for subjects with baseline titer \<1:10 Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the PPS; definitions are provided in the SAP. The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
Time frame: Day 8, Day 22, Day 43
GMT of HI Antibodies Against the H5N1 Strain
GMT pre-vaccination, 1 and 3 weeks post-vaccination 1, and 3 weeks and 6 months post-vaccination 2 Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the PPS; definitions are provided in the SAP. The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
Time frame: Day 1, Day 8, Day 22, Day 43, Day 202
GMFI of HI Antibodies Against the H5N1 Strain
GMFI 1 and 3 weeks post-vaccination 1, and 3 weeks and 6 months post-vaccination 2 compared to pre-vaccination (Day 1) Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the PPS; definitions are provided in the SAP. The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
Time frame: Day 1, Day 8, Day 22, Day 43, Day 202
Percentage of Subjects With HI Titers ≥1:40 Against the H5N1 Strain
Pre-vaccination, 1 and 3 weeks post-vaccination 1, and 3 weeks and 6 months post-vaccination 2 Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the PPS; definitions are provided in the SAP. The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
Time frame: Day 1, Day 8, Day 22, Day 43, Day 202
Percentage of Subjects With Seroconversion Against the H5N1 Strain
Seroconversion 1 and 3 weeks post-vaccination 1, and 3 weeks and 6 months post-vaccination 2, defined as a ≥4-fold increase in HI titer post-vaccination in those with pre-vaccination titer ≥1:10, or a post-vaccination HI titer ≥1:40 for subjects with baseline titer \<1:10 Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the PPS; definitions are provided in the SAP. The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
Time frame: Day 8, Day 22, Day 43, Day 202
GMT of HI Antibodies Against the H5N6 Strain
GMT 6 months post-vaccination 2
Time frame: Day 202
GMFI of HI Antibodies Against the H5N6 Strain
GMFI 6 months post-vaccination 2 compared to pre-vaccination (Day 1)
Time frame: Day 1, Day 202
Percentage of Subjects With HI Titers ≥1:40 Against the H5N6 Strain
6 months post-vaccination 2
Time frame: Day 202
Percentage of Subjects With Seroconversion Against the H5N6 Strain
Seroconversion 6 months post-vaccination 2, defined as a ≥4-fold increase in HI titer post-vaccination in those with pre-vaccination titer ≥1:10, or a post-vaccination HI titer ≥1:40 for subjects with baseline titer \<1:10
Time frame: Day 202
Frequency and Severity of Solicited Local and Systemic Adverse Events (AEs)
For 7 days following each vaccination
Time frame: Day 1 through Day 7 and Day 22 through Day 28
Frequency and Severity of Unsolicited AEs
For 3 weeks following each vaccination
Time frame: Day 1 through Day 43
Frequency of Serious AEs (SAEs), AEs Leading to Withdrawal, AEs of Special Interest (AESI) and Medically Attended AEs (MAAEs)
From vaccination until study completion
Time frame: Day 1 through Day 202
Subjects were enrolled between 18 July 2022 and 2 September 2022.
| Milestone | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| Started | 81 | 78 | 101 |
| Completed | 75 | 74 | 95 |
| Not completed | 6 | 4 | 6 |
| Withdrew: Adverse event | 1 | 0 | 0 |
| Withdrew: Death | 1 | 0 | 0 |
| Withdrew: Lost to follow-up | 0 | 3 | 3 |
| Withdrew: Protocol violation | 0 | 1 | 1 |
| Withdrew: Withdrawal by subject | 4 | 0 | 1 |
| Withdrew: Unable to obtain blood sample | 0 | 0 | 1 |
GMT pre-vaccination, 1 and 3 weeks post-vaccination 1, and 3 weeks post-vaccination 2 Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the per-protocol set (PPS); definitions are provided in the Statistical Analysis Plan (SAP). The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
| titer | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| Day 1 | 5.48 (5.07 to 5.92) | 5.55 (5.13 to 6.01) | 5.47 (5.12 to 5.85) |
| Day 8 | 20.39 (15.22 to 27.33) | 23.67 (17.47 to 32.06) | 7.97 (6.21 to 10.23) |
| Day 22 | 46.89 (34.62 to 63.50) | 66.73 (48.85 to 91.14) | 12.14 (9.30 to 15.85) |
| Day 43 | 58.16 (43.21 to 78.28) | 50.55 (37.21 to 68.68) | 30.76 (23.78 to 39.79) |
GMFI 1 and 3 weeks post-vaccination 1, and 3 weeks post-vaccination 2 compared to pre-vaccination (Day 1) Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the PPS; definitions are provided in the SAP. The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
| ratio | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| Day 8 / Day 1 | 3.71 (2.77 to 4.98) | 4.31 (3.18 to 5.84) | 1.45 (1.13 to 1.86) |
| Day 22 / Day 1 | 8.52 (6.29 to 11.54) | 12.13 (8.88 to 16.57) | 2.21 (1.69 to 2.88) |
| Day 43 / Day 1 | 10.54 (7.83 to 14.19) | 9.16 (6.74 to 12.45) | 5.58 (4.31 to 7.21) |
Pre-vaccination, 1 and 3 weeks post-vaccination 1, and 3 weeks post-vaccination 2 Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the PPS; definitions are provided in the SAP. The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
| % of participants | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| Day 1 | 0.0 (0.00 to 4.99) | 0.0 (0.00 to 5.44) | 1.1 (0.03 to 5.91) |
| Day 8 | 29.4 (18.98 to 41.71) | 39.1 (27.10 to 52.07) | 9.9 (4.62 to 17.95) |
| Day 22 | 60.8 (48.77 to 71.96) | 65.2 (52.79 to 76.29) | 20.7 (12.92 to 30.36) |
| Day 43 | 73.2 (61.41 to 83.06) | 59.1 (46.29 to 71.05) | 50.0 (39.39 to 60.61) |
Seroconversion 1 and 3 weeks post-vaccination 1, and 3 weeks post-vaccination 2, defined as a ≥4-fold increase in HI titer post-vaccination in those with pre-vaccination titer ≥1:10, or a post-vaccination HI titer ≥1:40 for subjects with baseline titer \<1:10 Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the PPS; definitions are provided in the SAP. The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
| % of participants | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| Day 8 | 28.4 (18.01 to 40.69) | 36.1 (24.16 to 49.37) | 8.9 (3.92 to 16.77) |
| Day 22 | 59.7 (47.5 to 71.12) | 63.6 (50.87 to 75.13) | 18.9 (11.41 to 28.51) |
| Day 43 | 71.0 (58.84 to 81.31) | 55.6 (42.49 to 68.08) | 47.2 (36.51 to 58.06) |
GMT pre-vaccination, 1 and 3 weeks post-vaccination 1, and 3 weeks and 6 months post-vaccination 2 Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the PPS; definitions are provided in the SAP. The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
| titer | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| Day 1 | 13.16 (10.91 to 15.87) | 15.54 (12.83 to 18.83) | 6.89 (5.86 to 8.11) |
| Day 8 | 115.14 (85.71 to 154.69) | 122.91 (90.05 to 167.75) | 14.81 (11.43 to 19.20) |
| Day 22 | 345.46 (255.76 to 466.61) | 428.42 (312.86 to 586.67) | 17.95 (13.59 to 23.71) |
| Day 43 | 333.37 (250.37 to 443.87) | 343.48 (253.50 to 465.40) | 23.15 (17.70 to 30.28) |
| Day 202 | 122.10 (93.95 to 158.67) | 99.22 (75.66 to 130.12) | 15.86 (12.43 to 20.25) |
GMFI 1 and 3 weeks post-vaccination 1, and 3 weeks and 6 months post-vaccination 2 compared to pre-vaccination (Day 1) Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the PPS; definitions are provided in the SAP. The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
| ratio | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| Day 8 / Day 1 | 11.13 (8.28 to 14.95) | 11.88 (8.70 to 16.21) | 1.43 (1.10 to 1.86) |
| Day 22 / Day 1 | 31.97 (23.67 to 43.18) | 39.65 (28.95 to 54.29) | 1.66 (1.26 to 2.19) |
| Day 43 / Day 1 | 30.78 (23.12 to 40.98) | 31.71 (23.40 to 42.97) | 2.14 (1.63 to 2.80) |
| Day 202 / Day 1 | 11.07 (8.52 to 14.38) | 8.99 (6.86 to 11.80) | 1.44 (1.13 to 1.84) |
Pre-vaccination, 1 and 3 weeks post-vaccination 1, and 3 weeks and 6 months post-vaccination 2 Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the PPS; definitions are provided in the SAP. The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
| % of participants | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| Day 1 | 13.2 (6.23 to 23.64) | 23.8 (13.98 to 36.21) | 2.3 (0.28 to 7.97) |
| Day 8 | 83.8 (72.90 to 91.64) | 81.3 (69.54 to 89.92) | 10.1 (4.73 to 18.33) |
| Day 22 | 91.9 (83.18 to 96.97) | 97.1 (89.92 to 99.65) | 12.6 (6.48 to 21.50) |
| Day 43 | 93.1 (84.53 to 97.71) | 90.9 (81.26 to 96.59) | 20.0 (12.10 to 30.08) |
| Day 202 | 82.9 (71.97 to 90.82) | 81.8 (70.39 to 90.24) | 9.6 (4.25 to 18.11) |
Seroconversion 1 and 3 weeks post-vaccination 1, and 3 weeks and 6 months post-vaccination 2, defined as a ≥4-fold increase in HI titer post-vaccination in those with pre-vaccination titer ≥1:10, or a post-vaccination HI titer ≥1:40 for subjects with baseline titer \<1:10 Note: The Overall Number of Participants Analyzed (N) represents the total number of participants in the PPS; definitions are provided in the SAP. The Number Analyzed (n) at each timepoint corresponds to the number of participants with an available serum analysis result for the relevant strain at that timepoint. Instances where n\<N reflect missing serum samples or non-evaluable results. All participants included in the Overall Number of Participants Analyzed contributed data to the analysis at one or more timepoints.
| % of participants | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| Day 8 | 77.8 (65.54 to 87.28) | 72.4 (59.10 to 83.34) | 8.0 (3.30 to 15.88) |
| Day 22 | 89.7 (79.93 to 95.76) | 96.8 (89.00 to 99.61) | 9.4 (4.15 to 17.71) |
| Day 43 | 89.6 (79.65 to 95.70) | 90.2 (79.81 to 96.30) | 13.4 (6.89 to 22.74) |
| Day 202 | 73.8 (61.46 to 83.97) | 75.4 (62.71 to 85.54) | 6.3 (2.06 to 13.99) |
GMT 6 months post-vaccination 2
| titer | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| GMT of HI Antibodies Against the H5N6 Strain | 21.18 (16.69 to 26.89) | 19.35 (15.20 to 24.64) | 10.05 (8.14 to 12.40) |
GMFI 6 months post-vaccination 2 compared to pre-vaccination (Day 1)
| ratio | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| GMFI of HI Antibodies Against the H5N6 Strain | 3.82 (3.01 to 4.85) | 3.49 (2.74 to 4.45) | 1.81 (1.47 to 2.24) |
6 months post-vaccination 2
| % of participants | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| Percentage of Subjects With HI Titers ≥1:40 Against the H5N6 Strain | 39.7 (28.03 to 52.30) | 30.3 (19.59 to 42.85) | 11.8 (5.79 to 20.57) |
Seroconversion 6 months post-vaccination 2, defined as a ≥4-fold increase in HI titer post-vaccination in those with pre-vaccination titer ≥1:10, or a post-vaccination HI titer ≥1:40 for subjects with baseline titer \<1:10
| % of participants | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| Percentage of Subjects With Seroconversion Against the H5N6 Strain | 37.3 (25.80 to 49.99) | 30.2 (19.23 to 43.02) | 9.6 (4.25 to 18.11) |
For 7 days following each vaccination
| Participants | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| Solicited AEs (Overall) | 54 | 48 | 67 |
| Solicited Local AEs | 51 | 38 | 60 |
| Solicited Local AEs - Severe | 0 | 2 | 0 |
| Solicited Systemic AEs | 26 | 34 | 36 |
| Solicited Systemic AEs - Severe | 2 | 1 | 2 |
| Analgesic/antipyretic Use | 8 | 5 | 13 |
For 3 weeks following each vaccination
| Participants | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| Unsolicited AEs (Overall) | 23 | 21 | 25 |
| Unsolicited AEs - Mild | 8 | 11 | 18 |
| Unsolicited AEs - Moderate | 14 | 9 | 7 |
| Unsolicited AEs - Severe | 1 | 1 | 0 |
From vaccination until study completion
| Participants | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| SAE | 3 | 3 | 4 |
| MAAE | 22 | 21 | 28 |
| AESI | 0 | 0 | 0 |
| AE leading to withdrawal from treatment | 0 | 0 | 1 |
| AE leading to withdrawal from study | 1 | 0 | 0 |
Collected over SAEs, AEs leading to withdrawal from the study, adverse events of special interest (AESIs), and MAAEs Day 1 through Day 202, other AEs Day 1 through Day 43. Non-serious events are listed at a 5% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Group 1 | 1/80 (1.3%) | 3/80 (3.8%) | 12/80 (15%) |
| Group 2 | 0/78 (0%) | 3/78 (3.8%) | 5/78 (6.4%) |
| Group 3 | 0/100 (0%) | 4/100 (4%) | 7/100 (7%) |
| Event | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| CholecystitisHepatobiliary disorders | 0/80 | 1/78 | 0/100 |
| Type 2 diabetes mellitusMetabolism and nutrition disorders | 0/80 | 1/78 | 0/100 |
| Mantle cell lymphomaNeoplasms benign, malignant and unspecified (incl cysts and polyps) | 0/80 | 1/78 | 1/100 |
| Hypertensive heart diseaseCardiac disorders | 1/80 | 0/78 | 0/100 |
| Brain neoplasmNeoplasms benign, malignant and unspecified (incl cysts and polyps) | 1/80 | 0/78 | 0/100 |
| SeizureNervous system disorders | 1/80 | 0/78 | 0/100 |
| Acute respiratory failureRespiratory, thoracic and mediastinal disorders | 1/80 | 0/78 | 0/100 |
| ArteriosclerosisVascular disorders | 1/80 | 0/78 | 0/100 |
| OsteoarthritisMusculoskeletal and connective tissue disorders | 0/80 | 0/78 | 1/100 |
| GlioblastomaNeoplasms benign, malignant and unspecified (incl cysts and polyps) | 0/80 | 0/78 | 1/100 |
| Event | Group 1 | Group 2 | Group 3 |
|---|---|---|---|
| COVID-19Infections and infestations | 7/80 | 3/78 | 3/100 |
| Injection site bruisingGeneral disorders | 5/80 | 3/78 | 4/100 |
| Age, Continuous(years) | Group 1 | Group 2 | Group 3 | Total |
|---|---|---|---|---|
| Mean | 52.8 ± 10.59 | 52.8 ± 10.67 | 47.9 ± 13.17 | 50.9 ± 11.88 |
| Age, Customized(Participants) | Group 1 | Group 2 | Group 3 | Total |
|---|---|---|---|---|
| Age Group — 18-49 years | 25 | 25 | 51 | 101 |
| Age Group — ≥50 years | 56 | 53 | 50 | 159 |
| Sex: Female, Male(Participants) | Group 1 | Group 2 | Group 3 | Total |
|---|---|---|---|---|
| Female | 52 | 46 | 55 | 153 |
| Male | 29 | 32 | 46 | 107 |
| Ethnicity (NIH/OMB)(Participants) | Group 1 | Group 2 | Group 3 | Total |
|---|---|---|---|---|
| Hispanic or Latino | 13 | 17 | 23 | 53 |
| Not Hispanic or Latino | 67 | 60 | 78 | 205 |
| Unknown or Not Reported | 1 | 1 | 0 | 2 |
| Race (NIH/OMB)(Participants) | Group 1 | Group 2 | Group 3 | Total |
|---|---|---|---|---|
| American Indian or Alaska Native | 0 | 0 | 0 | 0 |
| Asian | 1 | 2 | 2 | 5 |
| Native Hawaiian or Other Pacific Islander | 0 | 0 | 0 | 0 |
| Black or African American | 6 | 13 | 18 | 37 |
| White | 74 | 61 | 80 | 215 |
| More than one race | 0 | 1 | 1 | 2 |
| Unknown or Not Reported | 0 | 1 | 0 | 1 |
| Region of Enrollment(participants) | Group 1 | Group 2 | Group 3 | Total |
|---|---|---|---|---|
| United States | 81 | 78 | 101 | 260 |
| Influenza Vaccination Within Past 2 Years(Participants) | Group 1 | Group 2 | Group 3 | Total |
|---|---|---|---|---|
| Yes | 54 | 47 | 65 | 166 |
| No | 27 | 31 | 36 | 94 |
| Height(cm) | Group 1 | Group 2 | Group 3 | Total |
|---|---|---|---|---|
| Mean | 167.92 ± 8.613 | 167.16 ± 9.593 | 168.71 ± 11.246 | 168.00 ± 9.976 |
2 further baseline measures are reported on the registry.
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: Undecided
Ran from Jul 2022 to primary completion in Oct 2022, 3 months.
Results were first posted in May 2026, 3 years 6 months after primary completion. A results delay was requested in Aug 2023.
Of 86 industry-sponsored phase 2 interventional studies under Influenza, Human, half reached primary completion within 7 months of starting (the median), counting those still running; a quarter within 5 and three quarters within 14. This study's 3 months is below that.
Counting every sponsor, half of 122 studies reached it within 10 months; a quarter within 5 and three quarters within 19.
How these figures are worked out, and which studies are left out of them.
This study is completed, as verified in Oct 2025. You cannot join it, but the record below documents what was studied.
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