H5N1 InfluenzaPhase 4NCT07275060
Immunogenicity and Safety of 2 Doses of Avian Influenza A (H5N1) Vaccine Administered 3 vs. 8 Weeks Apart
A Phase 4 study testing H5N1 vaccine (Arepanrix) in people with H5N1 Influenza and H5N1 Virus, run by Canadian Immunization Research Network at 4 sites in Canada.
Trial summary
Given the recent circulation of avian influenza A(H5N1) clade 2.3.4.4b strains in birds and mammals in North America, Canada procured a supply of Arepanrix™ H5N1 for potential use in persons at high risk of highly pathogenic avian influenza exposure. Read more about this study
- Who is it for?
- Ages 18 to 59 yearsHealthy volunteers can take part
- Conditions the study is for
- H5N1 Influenza, H5N1 Virus, Avian Influenza
- What is being tested?
- H5N1 vaccine (Arepanrix)
- Type of treatment
- Vaccines
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 312 participants
- Where
- 4 sitesCanada
- Study dates
- 14 Oct 2025to 30 Sep 2027
- Phase
- Phase 4
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 59 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Individuals in stable health (defined as no new onset or exacerbation of pre-existing chronic disease three months prior to vaccination) 18-59 years of age.
- Able to comply with the trial procedures.
- Informed consent signed prior to trial-specific procedures.
- If a person is at risk of becoming pregnant, has practiced adequate contraception for 28 days prior to visit 1, and has a negative pregnancy test on the day of vaccination and has agreed to continue adequate contraception until 60 days after the final vaccination.
- Risk of pregnancy is defined as any cis woman and/or gender divergent individual assigned female at birth or with reproductive capacity who is sexually active with individuals with sperm-producing capabilities.
- Individual who are post-menopausal or permanently sterile (hysterectomy, bilateral salpingectomy) are not considered at risk of pregnancy. A post-menopausal state is defined as a no menses for 12 months.
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- Effective contraception methods are:
- Combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation:
- Oral
- Intravaginal
- Transdermal
- Progestogen-only hormonal contraception associated with inhibition of ovulation:
- Oral
- Injectable
- Implantable
- Intra-uterine device (IUD) with or without hormonal release.
- Vasectomised partner, provided that this partner is your sole sexual partner and that the vasectomised partner has received a medical assessment of the surgical success.
- Credible self-reported history of heterosexual abstinence prior to and for at least 28 days after the vaccine.
- Effective contraception methods are:
- Combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation:
- Oral
- Intravaginal
- Transdermal
- Progestogen-only hormonal contraception associated with inhibition of ovulation:
- Oral
- Injectable
- Implantable
- Intra-uterine device (IUD) with or without hormonal release.
- Vasectomised partner, provided that this partner is your sole sexual partner and that the vasectomised partner has received a medical assessment of the surgical success.
- Credible self-reported history of heterosexual abstinence prior to and for at least 28 days after the vaccine.
Who cannot join
- Any of the following:
- Receipt of avian influenza A(H5N1) vaccine anytime.
- Positive pregnancy test prior to vaccination, or breastfeeding.
- Receipt of immunoglobulins and/or any blood products within 3 months preceding the first dose of study vaccine and for one month after the last dose of study vaccine (except Rho D).
- Bleeding disorder or history of significant bleeding following IM injections or venipuncture.
- Any confirmed or suspected immunosuppressive or immunodeficient state; asplenia, or immunosuppressant medication within the past 6 months except short term oral steroids (≤14 days duration) or topical steroids.
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- A significant acute disease or temperature ≥38 Co within 24 hours prior to vaccination (temporary exclusion criteria, participants can return for evaluation to be randomized/ vaccinated 72 hours after symptoms resolve).
- Unstable chronic medical condition requiring ongoing follow-up and monitoring by a physician as determined by the investigator.
- History of anaphylaxis or allergy to any of the constituents or trace residues of the study vaccine, including egg protein.
- Receipt of non-study vaccine(s) 2 weeks prior to the study vaccine or planned 2 weeks after administration of the study vaccine.
Trial locations and contacts
4 sites in 1 country.
Canada4 sites
Canadian Center for Vaccinology
Halifax, Nova Scotia
Vaccine Study Centre of the McGill University Health Centre
Pierrefonds, Quebec, H9H 4Y6
CHU de Québec
Québec, Quebec, G1E 7G9
Vaccine Evaluation Center
Vancouver, British Columbia
About this study
Official title: Immunogenicity and Safety of 2 Doses of Avian Influenza A (H5N1) Vaccine Administered 3 vs. 8 Weeks Apart - A Multi-Center Non-Inferiority Placebo-Controlled Observer-Blinded Phase 2 Randomized Controlled Trial
Given the recent circulation of avian influenza A(H5N1) clade 2.3.4.4b strains in birds and mammals in North America, Canada procured a supply of Arepanrix™ H5N1 for potential use in persons at high risk of highly pathogenic avian influenza exposure.
This vaccine received regulatory approval in 2013, to be given in two doses at least 3 weeks apart. There is limited data on the effect of various intervals between the two doses on immunogenicity and tolerability. In this study two intervals between doses will be compared (3 vs. 8 weeks apart).
- Conditions
- H5N1 Influenza, H5N1 Virus, Avian Influenza, Avian Influenza A Virus
- Being tested
- H5N1 vaccine (Arepanrix), Saline (as a placebo)
- Keywords
- clinical trial, avian flu, H5N1, vaccine
- Medical subject headings
- Influenza in Birds
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
H5N1 vaccine (Arepanrix)Biological
Also called Arepanrix, GSK
The H5N1 (Arepanrix) vaccine will be administered according to the Product Monograph.
Saline (as a placebo)Other
Also called Normal Saline
Normal saline will be administered as a placebo according to the Product Monograph.
| Study group | Role | What they receive |
|---|---|---|
| Group 1: H5N1 vaccines administered 3 weeks apart | Active comparator | Two doses of the H5N1 vaccine administered 3 weeks apart.
Normal saline will be administered as a placebo at week 8. Receives: Biological: H5N1 vaccine (Arepanrix); Other: Saline (as a placebo) |
| Group 2: H5N1 vaccines administered 8 weeks apart | Active comparator | Two doses of the H5N1 vaccine administered 8 weeks apart
Normal saline will be administered as a placebo at week 3. Receives: Biological: H5N1 vaccine (Arepanrix); Other: Saline (as a placebo) |
What is being measured
The primary outcome is the main question the study is designed to answer.
Percentages of participants with seroprotection against the H5N1 2.3.4.4b clade vaccine given 3 vs. 8 weeks apart
Percentages of participants with seroprotection against the H5N1 2.3.4.4b clade 28 days following administration of 2 doses of avian influenza A(H5N1) vaccine given 3 vs. 8 weeks apart based on serologic outcomes at visit 4 (approximately week 12).
Seroprotection is defined as the proportion of subjects who were either seronegative prior to vaccination and have a protective post-vaccination HI titre of ≥ 1:40 or who were seropositive prior to vaccination and have at least a 4-fold increase in HI titre post-vaccination.
Measured: 28 days post-administration of 2 doses of avian influenza A (H5N1 (Approximately week 12).
Secondary outcomes (5)
Immunogenicity - Percentages of participants with seroconversion and the geometric mean fold rise against the H5N1 2.3.4.4b clade vaccine given 3 vs. 8 weeks apart.
Definition of Seroconversion rate: the proportion of subjects who were either seronegative prior to vaccination and have a protective post-vaccination HI titre of ≥ 1:40 or who were seropositive prior to vaccination and have at least a 4-fold increase in HI titre post-vaccination) as acceptable by regulators for approval of a Pandemic influenza Vaccine (22).
Definition of Geometric mean fold rise: the ratio of the post-vaccination geometric mean HI titre divided by the pre-vaccination geometric mean HI titre) acceptable by regulators for approval of a Pandemic influenza Vaccine (22).
Measured: 28 days post-administration of 2 doses of avian influenza A (H5N1)
Immunogenicity - GMT of HI against the H5N1 2.3.4.4b clade vaccine given 3 vs. 8 weeks apart.
GMT of HI against the H5N1 2.3.4.4b clade 28 days following administration of 2 doses of avian influenza A(H5N1) vaccine given 3 vs. 8 weeks apart.
Measured: 28 days post-administration of 2 doses of avian influenza A (H5N1) vaccine
Immunogenicity - Percentages of participants with seroprotection, seroconversion and the geometric mean fold rise against the H5N1 2.3.4.4b clade
Percentages of participants with seroprotection, seroconversion and the geometric mean fold rise against the H5N1 2.3.4.4b clade following administration of 1 dose of avian influenza A(H5N1) vaccine.
Measured: at baseline, at 3 weeks, at 8 weeks, 12 weeks, 26 weeks and through study completion (average of 1 year).
Immunogenicity - Percentages of participants with seroprotection, seroconversion and the geometric mean fold rise against the H5N1 2.3.4.4b clade
Percentages of participants with seroprotection, seroconversion and the geometric mean fold rise against the H5N1 2.3.4.4b clade 6 and 12 months after the first dose of avian influenza A(H5N1) vaccine given 3 vs. 8 weeks apart.
Measured: 6 and 12 months after the first dose of avian influenza A (H5N1) vaccine
Incidence of Grade 3 & 4 Adverse Events
The following AEFIs will be collected in all participants:
- Grade 3 solicited local and systemic adverse events in the 7 days following vaccine receipt;
- SAEs at any time after vaccine receipt during the study;
- MAAE at any time after vaccine receipt during the study,
- AESI at any time after vaccine receipt during the study;
- Provincially reportable AEFI at after vaccine receipt; and
- acceptability as measured by participant questionnaire.
Solicited adverse events and grading Grade 3 and 4 solicited local (injection-site) and systemic adverse events occurring during the 7-day follow-up period after each injection will be recorded.
Solicited local (injection-site) adverse events (Pain, redness and swelling at injection site).
Solicited systemic AEs, grade 3 and 4 will be recorded (Fatigue, fever - recorded, headache, nausea, diarrhea, vomiting, generalized muscle aches, joint pain and chills).
Measured: Up to 12 months after the first dose of avian influenza A (H5N1) vaccine
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted10 Dec 2025
- Study start14 Oct 2025
- Primary completion28 Feb 2027 (estimated)
- Study completion30 Sep 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for H5N1 InfluenzaStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 4
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 312 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Canadian Immunization Research Network
- Sponsor type
- Research network
- Collaborators
- Dalhousie University, IWK Health Centre, Public Health Agency of Canada (PHAC), Canadian Center for Vaccinology, CHU de Quebec-Universite Laval, Vaccine Evaluation Center, Canada, McGill University Health Centre/Research Institute of the McGill University Health Centre
- Responsible party
- Principal investigator, Joanne Langley, Canadian Immunization Research Network
- Investigators
- Joanne M Langley, Principal investigator, CIRN, Canadian Center for Vaccinology, Dalhousie University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07275060
- Sponsor's protocol ID
- CT27
- Status last verified
- Jan 2026
- First submitted
- 16 Nov 2025
- Last updated
- 16 Jan 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Study at a glance
From the registry record, last updated by the sponsor on 16 Jan 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Immunogenicity and Safety of 2 Doses of Avian Influenza A (H5N1) Vaccine Administered 3 vs. 8 Weeks Apart - A Multi-Center Non-Inferiority Placebo-Controlled Observer-Blinded Phase 2 Randomized Controlled Trial
- ClinicalTrials.gov ID
- NCT07275060
- Acronym / sponsor ID
- CT27
- Conditions
- H5N1 Influenza, H5N1 Virus, Avian Influenza, Avian Influenza A Virus
- Keywords
- clinical trial, avian flu, H5N1, vaccine
- Phase
- Phase 4
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 312 participants (estimated)
- Lead sponsor
- Canadian Immunization Research NetworkResearch network
- Collaborators
- Dalhousie University, IWK Health Centre, Public Health Agency of Canada (PHAC), Canadian Center for Vaccinology, CHU de Quebec-Universite Laval, Vaccine Evaluation Center, Canada, McGill University Health Centre/Research Institute of the McGill University Health Centre
- Study start
- 14 Oct 2025 (actual)
- Primary completion
- 28 Feb 2027 (estimated)
- Study completion
- 30 Sep 2027 (estimated)
- First posted
- 10 Dec 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Given the recent circulation of avian influenza A(H5N1) clade 2.3.4.4b strains in birds and mammals in North America, Canada procured a supply of Arepanrix™ H5N1 for potential use in persons at high risk of highly pathogenic avian influenza exposure.
This vaccine received regulatory approval in 2013, to be given in two doses at least 3 weeks apart. There is limited data on the effect of various intervals between the two doses on immunogenicity and tolerability. In this study two intervals between doses will be compared (3 vs. 8 weeks apart).
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Group 1: H5N1 vaccines administered 3 weeks apart | Active comparator | Biological: H5N1 vaccine (Arepanrix), Other: Saline (as a placebo)Two doses of the H5N1 vaccine administered 3 weeks apart. Normal saline will be administered as a placebo at week 8. |
| Group 2: H5N1 vaccines administered 8 weeks apart | Active comparator | Biological: H5N1 vaccine (Arepanrix), Other: Saline (as a placebo)Two doses of the H5N1 vaccine administered 8 weeks apart Normal saline will be administered as a placebo at week 3. |
Who may qualify
- Ages
- 18 to 59 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (30 listed)
- Individuals in stable health (defined as no new onset or exacerbation of pre-existing chronic disease three months prior to vaccination) 18-59 years of age.
- Able to comply with the trial procedures.
- Informed consent signed prior to trial-specific procedures.
- If a person is at risk of becoming pregnant, has practiced adequate contraception for 28 days prior to visit 1, and has a negative pregnancy test on the day of vaccination and has agreed to continue adequate contraception until 60 days after the final vaccination.
- Risk of pregnancy is defined as any cis woman and/or gender divergent individual assigned female at birth or with reproductive capacity who is sexually active with individuals with sperm-producing capabilities.
Key exclusion criteria (10 listed)
- Any of the following:
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| H5N1 vaccine (Arepanrix)Also: Arepanrix, GSKThe H5N1 (Arepanrix) vaccine will be administered according to the Product Monograph. | Biological | Group 1: H5N1 vaccines administered 3 weeks apart, Group 2: H5N1 vaccines administered 8 weeks apart |
| Saline (as a placebo)Also: Normal SalineNormal saline will be administered as a placebo according to the Product Monograph. | Other | Group 1: H5N1 vaccines administered 3 weeks apart, Group 2: H5N1 vaccines administered 8 weeks apart |
Primary outcome
Percentages of participants with seroprotection against the H5N1 2.3.4.4b clade vaccine given 3 vs. 8 weeks apart
Time frame: 28 days post-administration of 2 doses of avian influenza A (H5N1 (Approximately week 12).
Percentages of participants with seroprotection against the H5N1 2.3.4.4b clade 28 days following administration of 2 doses of avian influenza A(H5N1) vaccine given 3 vs. 8 weeks apart based on serologic outcomes at visit 4 (approximately week 12). Seroprotection is defined as the proportion of subjects who were either seronegative prior to vaccination and have a protective post-vaccination HI titre of ≥ 1:40 or who were seropositive prior to vaccination and have at least a 4-fold increase in HI titre post-vaccination.
5 secondary outcomes
Immunogenicity - Percentages of participants with seroconversion and the geometric mean fold rise against the H5N1 2.3.4.4b clade vaccine given 3 vs. 8 weeks apart.
Time frame: 28 days post-administration of 2 doses of avian influenza A (H5N1)
Immunogenicity - GMT of HI against the H5N1 2.3.4.4b clade vaccine given 3 vs. 8 weeks apart.
Time frame: 28 days post-administration of 2 doses of avian influenza A (H5N1) vaccine
Immunogenicity - Percentages of participants with seroprotection, seroconversion and the geometric mean fold rise against the H5N1 2.3.4.4b clade
Time frame: at baseline, at 3 weeks, at 8 weeks, 12 weeks, 26 weeks and through study completion (average of 1 year).
Immunogenicity - Percentages of participants with seroprotection, seroconversion and the geometric mean fold rise against the H5N1 2.3.4.4b clade
Time frame: 6 and 12 months after the first dose of avian influenza A (H5N1) vaccine
Incidence of Grade 3 & 4 Adverse Events
Time frame: Up to 12 months after the first dose of avian influenza A (H5N1) vaccine
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 16 Jan 2026.
- Website with information about study recruitmentLink provided by the sponsor.
- Individual participant dataSharing planned: Undecided
Related trials for H5N1 Influenza
RecruitingPhase 1
Study of Different Formulations of Vaccines Encoding the RSV Monovalent Antigen or the Flu H5 Antigen in Participants 18 to 49 Years of Age
Respiratory Syncytial Virus (RSV), Influenza A(H5N1)
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Joanne M Langley principal investigator
CIRN, Canadian Center for Vaccinology, Dalhousie University
4 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 4 study testing H5N1 vaccine (Arepanrix) in people with H5N1 Influenza and H5N1 Virus, run by Canadian Immunization Research Network at 4 sites in Canada.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 30 inclusion and 10 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 16 Jan 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 4 sites in Canada. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 4 studies take place after a treatment is approved, to learn more about its long-term benefits and risks in everyday use.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Percentages of participants with seroprotection against the H5N1 2.3.4.4b clade vaccine given 3 vs. 8 weeks apart (time frame: 28 days post-administration of 2 doses of avian influenza A (H5N1 (Approximately week 12).). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 16 Jan 2026; AzTrials last refreshed its copy on 8 Nov 2026.