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Study of Influenza Vaccine Effects on Immune Response in the Nose and Airways in Adults Seeking Protection Against Seasonal Flu

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What is this trial about?

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

This study examines the effects of influenza vaccination on immune responses in adults who plan to receive their seasonal flu shot. The vaccines being studied include Flucelvax, VAXIGRIPTETRA, and INFLUVAC TETRA, which are all approved vaccines designed to protect against seasonal influenza virus strains. These vaccines contain inactivated or surface parts of different influenza virus strains and are given as a single injection into the muscle. The immune system is the body's natural defense against infections, and this research focuses on understanding how vaccination affects specific immune cells called memory lymphocytes, which are white blood cells that help the body remember and fight off infections it has encountered before.

The purpose of this study is to examine how flu vaccination impacts two types of immune responses: resident memory immune cells found in the nasal lining and peripheral memory immune cells in the blood that can travel to the respiratory system, which includes the nose, throat, and lungs. Researchers want to understand whether getting a flu vaccine in the arm affects the immune defenses located directly in the nose and airways, where flu viruses typically enter the body. This information could help scientists better understand how flu vaccines work and potentially improve future vaccine strategies.

Participants in this study will receive one of the approved seasonal flu vaccines as they normally would during flu season. Before and after receiving the vaccine, researchers will collect samples from the nose and blood to measure changes in immune cell populations and markers that indicate how these cells move to different parts of the body. The study will also look at antibody levels, which are proteins that help neutralize viruses, and examine gene activity related to immune responses. The research is expected to begin enrolling participants in October 2025 and continue until April 2026.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Receiving the influenza vaccine

    Your participation begins when you receive the influenza vaccine. The vaccine will be administered as a single dose through an intramuscular injection, which means the injection is given into a muscle.

    One of three approved influenza vaccines will be used. All three vaccines are designed to protect against seasonal flu and contain inactivated (killed) virus components that help your body build immunity.

    The vaccine is provided in a pre-filled syringe and is given as a suspension for injection.

  2. Step 2

    Sample collection before vaccination

    Before you receive the vaccine, samples will be collected from you. These samples are necessary to measure your immune responses at the starting point.

    The collection will include nasal samples to examine immune cells in your nasal mucosa (the lining inside your nose) and blood samples to examine immune cells circulating in your bloodstream.

    These samples will be analyzed to determine the frequency of specific immune cells called resident memory lymphocytes in your nasal area and peripheral memory lymphocytes in your blood. These are cells that help your body remember and fight infections.

  3. Step 3

    Sample collection after vaccination

    After you have received the vaccine, additional samples will be collected from you at specified time points.

    Similar to the initial collection, nasal samples and blood samples will be taken to measure changes in your immune responses following vaccination.

    The samples will be used to assess how the vaccine affects the immune cells in your nasal mucosa and in your bloodstream, specifically looking at changes in the frequency of memory immune cells and markers that indicate their ability to migrate to respiratory tissues.

  4. Step 4

    Laboratory analysis of immune responses

    Your samples will be analyzed in the laboratory to measure several aspects of your immune response to the influenza vaccine.

    The analysis will include measuring the frequency of resident memory T and B lymphocytes in your nasal cavity. These are specialized immune cells that remain in the nasal area to provide local protection.

    Additionally, the percentage of specific migration markers on peripheral memory lymphocytes will be measured. These markers indicate the ability of immune cells in your blood to travel to respiratory tissues.

    The laboratory will also measure anti-influenza antibody levels and neutralizing antibody titers in both your nasal mucosa and blood serum. Antibodies are proteins produced by your immune system that help neutralize the virus.

    Further analysis will examine the cellular immune response specific to influenza and the expression of genes involved in your immune response.

  5. Step 5

    Comparison of results

    The main focus of the trial is to compare your immune responses before and after receiving the influenza vaccine.

    The variation in frequency of resident memory lymphocytes in your nasal mucosa and the expression of migration markers on peripheral memory lymphocytes will be calculated by comparing the measurements taken before vaccination with those taken after vaccination.

    Correlations will be examined between the frequency of nasal resident memory lymphocytes, the percentage of migration markers on peripheral memory lymphocytes, antibody levels in mucosa and serum, the cellular response to influenza, and the expression of immune-related genes.

    This comparison will help determine how intramuscular influenza vaccination affects local immune responses in the nasal area and systemic immune responses in the bloodstream.

Who can join the trial?

4 criteria

  • You must have decided to receive a flu vaccination, which is a shot that helps protect you against the seasonal influenza virus
  • You must be an adult, meaning 18 years of age or older
  • You must be willing to sign a consent form, which is a document that shows you agree to take part in the study
  • Both men and women can participate in this study

Who cannot join the trial?

3 criteria

  • The study has not provided specific exclusion criteria, which are reasons why someone cannot participate in this clinical trial
  • You should contact the study team directly to learn about any specific health conditions, medications, or other factors that might prevent you from joining this study
  • Generally, clinical trials may exclude people based on certain health problems, use of specific medicines, or other medical situations, but these details are not available in the current study information
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Investigated drugs

Influenza vaccine is a vaccine that helps protect against the flu. It works by teaching your immune system to recognize and fight the influenza virus. In this study, researchers are looking at how this vaccine affects immune cells in your nose and respiratory system to better understand how the body develops protection against flu infections.

What is already known about the treatment

Influenza Vaccine – This is a seasonal vaccine given as an injection into the muscle or sometimes as a nasal spray to protect adults against the flu virus. The vaccine works by introducing harmless pieces or weakened forms of the influenza virus into the body, which trains the immune system to recognize and fight the actual virus if exposed to it later. It stimulates both local immune memory cells in the nasal passages and circulating immune cells in the bloodstream that can quickly respond to influenza infection. This vaccine is widely approved and recommended annually for adults to prevent seasonal influenza and reduce the severity of illness if infection occurs.

Investigated diseases

Seasonal Influenza – Seasonal influenza is a viral infection caused by influenza viruses that affects the respiratory system. The disease typically begins suddenly with fever, muscle aches, headache, and fatigue. As the infection progresses, respiratory symptoms such as cough, sore throat, and nasal congestion develop. The virus spreads easily from person to person through droplets when infected individuals cough or sneeze. Most people recover within one to two weeks as their immune system fights off the infection. The body develops immune responses both in the blood and in the respiratory tract lining to combat the virus.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-521217-46-00Protocol code24CH249Estimated enrolment30 patientsSponsorCentre Hospitalier Universitaire De Saint Etienne

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