Study of H5N8 influenza vaccine in adults previously vaccinated with H5N1/MF59 vaccine compared to those never vaccinated with H5 vaccine

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What is this study about?

This clinical trial examines a vaccine for Avian Influenza, specifically focusing on the H5N8 strain. The study uses a Zoonotic Influenza Vaccine that contains inactivated virus particles with special additives to boost the immune response. The vaccine is given as an injection into the muscle.

The purpose of the study is to evaluate how well the vaccine works in two different groups of people: those who received a similar flu vaccine about 20 years ago and those who have never received this type of vaccine before. The study will measure how the body’s immune system responds to the vaccine by checking for protective substances in the blood.

Participants will receive two doses of the vaccine over a period of 28 days. Blood samples will be collected at various times to measure the immune response. The total duration of participation in the study will be approximately two months, during which time participants will need to attend several clinic visits for vaccinations and health checks.

1 Initial vaccination visit

Your first visit includes receiving the first dose of the H5N8 influenza vaccine through an injection in the muscle

Before vaccination, a brief medical check will be performed to confirm your eligibility

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

2 First follow-up

Visit occurs 7 days after first vaccination

Blood sample will be taken to measure your body’s immune response to the vaccine

3 Second follow-up

Visit occurs 28 days after first vaccination

Blood sample will be taken to measure your body’s immune response to the vaccine

4 Second vaccination visit

You will receive the second dose of the H5N8 influenza vaccine

This occurs on day 28 after your first vaccination

5 Third follow-up

Visit occurs 7 days after second vaccination (day 35 of study)

Blood sample will be taken to measure your body’s immune response to the vaccine

6 Final follow-up

Visit occurs 28 days after second vaccination (day 56 of study)

Final blood sample will be taken to measure your body’s immune response to the vaccine

This completes your participation in the study

7 Safety monitoring

Any significant medical events will be monitored throughout the study period

The total duration of your participation will be approximately 2 months

Who Can Join the Study?

Be willing and able to follow study requirements, such as reporting side effects and attending follow-up visits
Provide written informed consent and be able to understand the consent form
Be between 40 and 75 years old when receiving the study treatment
Be in stable medical condition. People with controlled chronic conditions like high blood pressure or heart disease may participate if their condition is stable
Women who cannot become pregnant may participate if they have had:
- Surgical removal of the uterus (hysterectomy)
- Surgical removal of both ovaries (bilateral oophorectomy)
- Surgical removal of both fallopian tubes (bilateral salpingectomy)
- Gone through menopause (no menstrual periods for 12 months)
Women who can become pregnant must:
- Use effective birth control from 1 month before treatment until study end
- Not be pregnant when receiving study treatment
For participants who have previously received H5N1 vaccine: Must have received two or three doses of M59-adjuvanted H5N1 vaccine in specific previous studies
For participants who have never received H5N1 vaccine: Must have never received any H5N1 or H5-containing vaccine

Who Cannot Join the Study?

Age below 18 years or above 60 years
History of severe allergic reactions to any influenza vaccines or their components
Currently pregnant or breastfeeding women
Participation in other clinical trials within the last 30 days
Active infection or fever (temperature above 38°C/100.4°F) at the time of vaccination
Weakened immune system due to disease or medications
History of Guillain-Barré syndrome (a rare disorder where the body’s immune system attacks the nerves)
Received any other vaccinations within 30 days before the study
Chronic medical conditions that are not well controlled
Blood disorders or taking blood-thinning medications
History of severe reactions to eggs or egg products (as vaccines may be produced using egg-based technology)
Mental conditions that may interfere with following study procedures
Drug or alcohol abuse within the past year
Any condition that, in the opinion of the study doctor, makes participation unsafe

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
Uuaklkaeum Oh Alzmoqz	Edegem	Belgium
Agfkerc Oisiubdexlh Uxqmrmvtinatf Szsrtn	Siena	Italy

Trial status

Country	Status	Recruitment Start
Belgium	Not recruiting	18.08.2025
Italy	Not recruiting	18.08.2025

Trial locations

Seqirus H5N8 influenza vaccine
This is a vaccine designed to protect against the H5N8 strain of avian (bird) influenza. It is being studied to understand how well it works in protecting people against this specific type of flu virus.

Novartis H5N1 influenza vaccine
This is an earlier version of a vaccine that was designed to protect against the H5N1 strain of avian influenza. Some participants in the trial received this vaccine approximately 20 years before the current study, while others have never received it. The study compares how these two groups respond to the new H5N8 vaccine.

MF59
This is an adjuvant (an ingredient added to vaccines) that helps strengthen the body’s immune response to the vaccine. It is used in combination with the H5N1 vaccine to make it more effective.

Avian Influenza – A viral infection primarily affecting birds that can occasionally spread to humans through close contact with infected poultry. The disease begins with flu-like symptoms including fever, cough, body aches, and respiratory difficulties. In humans, it typically develops rapidly, causing severe respiratory symptoms within the first few days of infection. The virus belongs to the influenza A family and has several strains, with H5N1 and H5N8 being notable variants that can affect humans. The infection affects the respiratory system and can cause inflammation in the airways and lungs. The condition is distinct from seasonal human influenza, though it may present with similar initial symptoms.

Trial ID:

2025-522116-16-00

Protocol code:

FLU-SEQ

Trial Phase:

Therapeutic confirmatory (Phase III)

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Study of H5N8 influenza vaccine in adults previously vaccinated with H5N1/MF59 vaccine compared to those never vaccinated with H5 vaccine

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?