Study of H5N8 Influenza Vaccine Response in Adults Previously Vaccinated with H5N1 Vaccine Compared to Those Never Vaccinated Against H5 Influenza

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What is this study about?

This study focuses on testing a vaccine against zoonotic influenza, specifically the H5N8 strain of the virus. The vaccine being tested is a suspension that is injected into the muscle and contains inactivated virus particles combined with an adjuvant called MF59, which helps strengthen the immune response.

The purpose of the study is to examine how well the vaccine works in two different groups of people: those who previously received a different flu vaccine (H5N1) in 2009, and those who have never received this type of vaccine before. The vaccine will be given as two doses over a period of about two months.

During the study, participants will receive injections of the vaccine and have blood samples taken to measure their body’s immune response to the vaccine. The blood tests will check for protective substances called antibodies that the body produces to fight against both the specific virus strain in the vaccine and other similar strains of the flu virus. The total duration of participation in the study will be approximately two months, with several visits to the clinic for vaccinations and blood sampling.

1 Initial vaccination visit

You will receive the first dose of H5N8 influenza vaccine through an injection in your muscle

A blood sample will be taken to check your initial antibody levels

The medical team will evaluate your health status before administering the vaccine

2 First follow-up – Day 7

You will visit the clinic for a blood sample collection

The medical team will check your response to the first vaccine dose

3 Second follow-up – Day 28

You will visit the clinic for another blood sample collection

The medical team will evaluate your antibody response to the first vaccine dose

4 Second vaccination – Day 28

You will receive the second dose of the H5N8 influenza vaccine

The medical team will evaluate your health status before administering the vaccine

5 Third follow-up – Day 35

You will visit the clinic for a blood sample collection

The medical team will check your response to the second vaccine dose

6 Final follow-up – Day 56

You will visit the clinic for the final blood sample collection

The medical team will evaluate your final antibody response to both vaccine doses

This marks the completion of your active participation in the study

7 Safety monitoring

The medical team will monitor any serious health events throughout the study period

You should report any significant health changes to the study team

Who Can Join the Study?

Must be between 35 and 70 years old at the time of receiving the study treatment
Must be in overall good health, as determined by medical evaluation
Must be able and willing to follow study requirements (such as reporting side effects and attending follow-up visits)
Must be medically stable. People with stable chronic conditions like high blood pressure or heart disease may participate if their condition is well-controlled
Must have a Body Mass Index (BMI) less than 18.0 or greater than 35.0 kg/m² (BMI is a measure of body fat based on height and weight)
Female participants must be either:
- Not able to have children (due to surgery or menopause), or
- Using effective birth control from 1 month before study start and throughout the study
- Not pregnant at the start of the study (confirmed by pregnancy test)
Must be able to understand and sign an informed consent form before any study procedures
For some participants: Must have received the PanFluVac H5N1 Matrix M vaccine in a 2009 Phase I study

Who Cannot Join the Study?

Age below 18 or above 60 years
Known allergy or severe reaction to any influenza vaccines in the past
History of Guillain-Barré syndrome (a rare disorder where the immune system attacks the nerves)
Pregnancy or breastfeeding
Participation in another clinical trial in the past 30 days
Any severe chronic illness that is not well controlled
Active infection or fever above 38°C (100.4°F) at the time of vaccination
Taking medications that suppress the immune system
History of severe allergic reactions requiring medical intervention
Blood disorders or conditions that make you bleed or bruise easily
Any vaccination in the past 30 days
Current diagnosis of cancer or undergoing cancer treatment
Received blood products or immunoglobulins (antibody treatments) in the past 3 months
Any condition that, in the opinion of the study doctor, might interfere with the study results

Where you can join this trial?

Verified and Recommended Sites

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Verified Sites

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Other Sites

Site Name	City	Country	Status
Hpuvg Bhrsxu Hy	Bergen	Norway

Trial status

Country	Status	Recruitment Start
Norway	Not recruiting	01.09.2025

Trial locations

MF59 adjuvanted zoonotic influenza vaccine (H5N8)
This is a vaccine designed to protect against the H5N8 strain of bird flu. It contains an adjuvant called MF59, which helps boost the immune system’s response to the vaccine. Adjuvants are substances that help vaccines work more effectively.

Matrix M adjuvanted virosomal influenza (H5N1) vaccine
This is a previously administered vaccine that protects against the H5N1 strain of bird flu. It uses Matrix M as an adjuvant and employs virosomal technology, which means the vaccine components are delivered in tiny, virus-like particles to better stimulate the immune system.

Influenza A virus H5N8 – A type of avian influenza virus that can cause respiratory disease in birds and occasionally infect humans. The virus belongs to the influenza A subtype H5 and primarily circulates among wild birds and poultry. It spreads through respiratory droplets and direct contact with infected animals. When human infection occurs, it typically causes symptoms similar to seasonal flu, including fever, cough, and respiratory difficulties.

Influenza A virus H5N1 – A strain of avian influenza that naturally occurs in wild waterfowl and can infect domestic poultry. The virus can occasionally cross species barriers to infect humans through close contact with infected birds. It belongs to the influenza A virus family and has several genetic variations called clades. When infection occurs, it typically begins with flu-like symptoms including fever, cough, and muscle aches.

Viral Disease – An illness caused by the presence and multiplication of a virus in a host organism’s body. Viruses enter cells of the body and use the cell’s own mechanisms to multiply themselves. The infection can affect various body systems depending on the type of virus. Common symptoms may include fever, fatigue, muscle aches, and specific symptoms related to the affected organ system.

Trial ID:

2025-522593-36-00

Protocol code:

SEQVAC1

Trial Phase:

Therapeutic confirmatory (Phase III)

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Study of H5N8 Influenza Vaccine Response in Adults Previously Vaccinated with H5N1 Vaccine Compared to Those Never Vaccinated Against H5 Influenza

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?