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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

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What is this trial about?

A plain-language summary of the goals, design and what participants do

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.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 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. Step 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. Step 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. Step 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. Step 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. Step 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. Step 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 trial?

10 criteria

  • 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 trial?

14 criteria

  • 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
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Investigated drugs

  • 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.

What is already known about the treatment

  • MF59-adjuvanted H5N8 influenza vaccine

    An injectable vaccine developed by Seqirus for protection against zoonotic influenza virus strain H5N8. This vaccine contains the MF59 adjuvant, which helps enhance the immune response and improve vaccine effectiveness. It is being studied in Phase IV clinical trials to evaluate immune responses in adults, particularly comparing those previously vaccinated with H5N1 vaccines to those who have never received H5 influenza vaccines. The vaccine represents an important development in preparing for potential pandemic influenza strains that could spread from birds to humans.

  • Matrix M-adjuvanted H5N1 virosomal influenza vaccine

    A previously administered injectable vaccine containing the Matrix M adjuvant system and virosomal technology for protection against the H5N1 bird flu strain. This vaccine was used in 2009 as part of pandemic preparedness efforts, utilizing special adjuvant technology to boost immune response against the potentially dangerous avian influenza virus. The vaccine's long-term immunological effects are being studied to understand how prior vaccination affects responses to newer influenza vaccines.

Investigated diseases

  • 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 detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-522593-36-00Protocol codeSEQVAC1Estimated enrolment180 patientsSponsorHelse Bergen HF

sourced from the EU Clinical Trials Register and site verification

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