Ongoing, recruitingTherapeutic use (Phase IV)Interventional

Phase IV multicenter immunogenicity and safety study of the Seqirus licensed zoonotic influenza vaccine (H5N8) in adults immunized with an H5N1/MF59 influenza vaccine, approximately 20 years before the trial, compared to H5 naive adult participants.

This study is testing a new vaccine for bird flu (H5N8) in adults. We're interested in how well your immune system responds to this vaccine. We'll be looking at people who received an older, similar bird flu vaccine (H5N1) about 20 years ago, and comparing them to people who have never had a bird flu vaccine before. The main goal is to understand how much protection the new vaccine offers. We will be checking your blood to see how many protective substances (antibodies) your body makes against the flu virus after getting the vaccine. This will help us understand if the new vaccine works effectively for different groups of people.

At a glance

Status

Ongoing, recruiting

Phase

Therapeutic use (Phase IV)

Sponsor

University Of Antwerp

Enrolment target

Start

06 Oct 2025

Avian Influenza

What is this study about?

This study is a medical research project focused on a type of flu called "bird flu" or "avian influenza." Specifically, we're looking at a new vaccine designed to protect against a particular strain known as H5N8. The main purpose is to understand how well this vaccine helps your body build up its defences against the virus.

We're especially interested in two groups of adult participants. One group will be adults who received a similar bird flu vaccine (H5N1) about 20 years ago. The other group will be adults who have not had any previous bird flu vaccination. By comparing these two groups, scientists can learn if having an older vaccine changes how your body reacts to the new one.

Ultimately, this research helps us understand the vaccine's effectiveness and how long protection might last, which is very important for public health. Because bird flu is a concern that can sometimes affect humans, understanding how different vaccines work is key to being prepared.

Key takeaways

This study assesses a new bird flu (H5N8) vaccine in adults.
It compares those vaccinated 20 years ago with those never vaccinated for bird flu.
Participation involves vaccine doses, blood tests, and clinic visits.
The study lasts approximately two months.
It helps understand vaccine effectiveness and immune response.

Who may be eligible?

To be considered for this study, you need to be an adult, aged 18 or older.

We are looking for two main groups of people. One group includes adults who received a specific bird flu vaccine (H5N1) roughly 20 years ago. The other group is for adults who have never had any bird flu vaccination.

More specific health checks will be done by the study doctors to make sure it's safe for you to take part and that you fit the study's requirements.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

Are you 18 years old or older?
Did you receive an H5N1 bird flu vaccine around 20 years ago, or have you never received any bird flu vaccine?
Are you able to attend clinic appointments for blood tests over approximately two months?
Are you a UK resident generally in good health? (Further checks will be made by study doctors)

Answer every question to see your result.

What does participation involve?

If you decide to take part, you'll receive the new bird flu vaccine (H5N8) as an injection. The study will involve several visits to the clinic over a period of about two months. During these visits, especially on Day 0 (the start), Day 28, and Day 56, we will take blood samples. These blood tests help us measure how your body is responding to the vaccine by checking for protective substances called antibodies.

You might also have additional blood tests on other days, such as Day 7 and Day 35, to track these responses more closely. In total, you would be followed for just under two months from your first dose. You can stop participating at any time if you change your mind.

Potential risks and benefits

Potential benefits of taking part could include contributing to important medical knowledge about bird flu vaccines, which may help protect people in the future. You will also receive a new vaccine. As with any vaccine, there might be some risks, such as mild side effects like soreness at the injection site, tiredness, or a low-grade fever. More serious reactions are very rare, but will be carefully monitored. You are free to withdraw from the study at any time, for any reason, without affecting your regular medical care.

Locations (2)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

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Unverified
Italy
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Unverified
Belgium

Common questions

What is bird flu?

Bird flu, or avian influenza, is a type of flu virus that usually infects birds. Sometimes, it can spread to humans.

What is an "H5N8" vaccine?

H5N8 refers to a specific type of bird flu virus. This vaccine is designed to help your body fight against that particular strain.

Why is this study looking at people who had a vaccine 20 years ago?

Scientists want to understand if having an older bird flu vaccine changes how your body reacts to a new, different bird flu vaccine.

Will I get sick after getting the vaccine?

Modern vaccines are designed to be safe. You might experience mild side effects like a sore arm or feeling a bit tired, similar to a regular flu shot. Serious reactions are rare.

How long will I need to be involved in the study?

Your participation will last for about two months from when you get your first vaccine dose.