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Safety and immune response of OVX836C2 vaccine compared with drug combination in healthy adults with influenza

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What is this trial about?

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

Influenza is a contagious respiratory illness that can cause fever, cough, muscle aches, and sometimes serious complications. This study evaluates a new vaccine that mixes an inactivated flu vaccine called GC IIV with a protein‑based component known as OVX836, and compares it with the individual components, a standard flu vaccine named Vaxigrip, and a placebo (a simple saline solution). All injections are given by intramuscular route, meaning the medicine is placed into the muscle using a short needle.

The main aim of the trial is to assess the safety and immune response of the mixed vaccine. Participants receive a single injection and are observed for a short period right after the shot. They then return for follow‑up visits a few weeks later and again several months later to check for any side effects and to see how well the body has responded to the vaccine.

During the study, volunteers are asked to report any local reactions such as soreness at the injection site and systemic symptoms like fever or fatigue. Small blood samples are taken to measure the level of antibodies—proteins that help the immune system recognize and fight the flu virus—and to evaluate other immune cells. Any serious problems that arise are recorded and reviewed throughout the study period.

The research process

The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Day 1: receive study injection

    After enrollment you will be randomly assigned to one of five groups. you will receive a single intramuscular injection in the upper arm.

    The injection may contain:

    - gc-iiv (an inactivated influenza vaccine) with 15 µg of each hemagglutinin (h3n2, h1n1, and b strains).

    - ovx836 (a protein based vaccine) with 480 µg.

    - both gc-iiv and ovx836 mixed together (the combo vaccine).

    - gc-iiv alone.

    - ovx836 alone.

    - or the licensed reference vaccine vaxigrip with 15 µg of each hemagglutinin.

    Only one of these formulations will be given, according to the random assignment.

  2. Step 2

    Post‑injection observation

    You will remain in the clinic for about 30 minutes after the injection so staff can watch for any immediate reactions.

  3. Step 3

    Record local and systemic symptoms for 7 days

    For the next seven days you will keep a diary of any symptoms such as pain, redness or swelling at the injection site, fever, headache, muscle aches, or fatigue.

    These are called solicited symptoms and are collected to evaluate short‑term safety.

  4. Step 4

    Monitor for unsolicited adverse events for 28 days

    During the first 28 days after the injection you should note any health problems that were not listed in the diary, such as unexpected illness or medical visits.

    These are called unsolicited adverse events and will be reported at study visits.

  5. Step 5

    Day 8 clinic visit

    On day 8 you will return to the clinic for a blood draw.

    The sample will be used to measure the cell‑mediated immune response (how your immune cells react to the vaccine).

  6. Step 6

    Day 29 clinic visit

    On day 29 you will have another blood draw to determine antibody levels against the three influenza strains.

    The visit also includes safety laboratory tests and a review of any symptoms experienced during the first month.

  7. Step 7

    Day 180 final visit

    Approximately six months after the injection (day 180) you will attend a final clinic visit.

    A blood sample will be taken to assess long‑term immunity and to complete the safety evaluation.

  8. Step 8

    Report serious health events at any time

    If you experience a serious medical problem at any point during the study, you must inform the study team immediately, regardless of the timing.

Who can join the trial?

5 criteria

  • Provide a signed document that shows you understand the study and agree to take part (written informed consent).
  • Be a man or woman who is generally healthy, as confirmed by a review of your past health records (medical history) and a physical check‑up (medical examination). If you could become pregnant, you must follow additional pregnancy‑related rules.
  • Be between 18 and 49 years old, including the start and end ages.
  • Be able to stay in the study for its whole length, attend all required visits, and follow the instructions given by the study staff.
  • Be able to use an electronic diary (a simple app on a phone or tablet) to record your daily information during the trial (eDiary).

Who cannot join the trial?

27 criteria

  • Body mass index (BMI) of 19 or lower, or 35 or higher (BMI measures body size using weight and height) disqualifies you.
  • Having too much water in the body (hyperhydration), too much sodium (hypernatremia), or too much chloride (hyperchloremia) excludes you.
  • If you received another vaccine within the past 3 months (for live vaccines) or within the past 1 month (for inactivated vaccines), you cannot join.
  • Planning to get any other vaccines during the first 28 days after the study vaccine also excludes you.
  • Taking any experimental or non‑approved drug or vaccine in the past 3 months, or planning to take one during the study, makes you ineligible.
  • Being enrolled in another clinical study now, or planning to join another study during this trial, disqualifies you.
  • Having received blood, blood parts, or immune‑boosting proteins (immunoglobulins) in the past 3 months, or planning to receive them, excludes you.
  • Donating 450 mL (about one pint) or more of blood within one month before screening or during the study is not allowed.
  • Having an acute illness or fever (temperature above 38.0 °C/100.4 °F) on the day of vaccination prevents participation.
  • A past or current serious nervous‑system disorder, seizure disorder, or Guillain‑Barré syndrome (a condition where the immune system attacks nerves) excludes you.
  • Behavioral, thinking, or psychiatric problems (such as depression, mania, bipolar disorder, or schizophrenia) that the investigator thinks will interfere with the study make you ineligible.
  • Anyone who has already received the OVX836 vaccine, at any dose, cannot participate.
  • Recent alcohol abuse (within the last 6 months), smoking more than 10 cigarettes per day, or current vaping disqualifies you.
  • Use of recreational or illegal drugs also excludes you.
  • Current or unstable lung problems—including asthma, chronic obstructive pulmonary disease (COPD), interstitial lung disease, pulmonary hypertension, cystic fibrosis, or acute respiratory infections—make you ineligible.
  • Taking medicines that can affect the immune system, such as high‑dose steroids, radiation therapy, chemotherapy, certain anti‑inflammatory drugs, interferon, immune‑modulating drugs, or allergy shots, disqualifies you.
  • Severe allergy or a strong reaction to any vaccine or its ingredients—especially egg proteins or the antibiotic kanamycin—excludes you.
  • Any condition that makes an injection into the muscle (intramuscular injection) unsafe prevents participation.
  • Any illness that the investigator believes could affect the study results or increase your risk makes you ineligible.
  • Employees of the study sponsor, study site staff, or their immediate family members (spouse, parent, child, or sibling) cannot join.
  • Having received an influenza vaccine within the past 6 months, or planning to receive one during the study, excludes you.
  • Being pregnant or breastfeeding makes you ineligible.
  • Known or suspected problems with the immune system (immunodeficiency) disqualify you.
  • Having a history of autoimmune diseases (where the body attacks its own tissues) excludes you.
  • Uncontrolled medical conditions such as diabetes, high blood pressure, heart disease, kidney disease, or liver disease make you ineligible.
  • Known or suspected infection with HIV, hepatitis B, or hepatitis C excludes you.
  • Abnormal results on safety laboratory tests (blood tests, etc.) prevent participation.
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Investigated drugs

  • GC FLU

    is an inactivated influenza vaccine that contains three different flu viruses (H3N2, H1N1, and influenza B). The viruses are killed so they cannot cause illness, but they still teach the immune system to recognize and fight the real flu. It is given as an injection into the muscle.

  • OVX836

    is an experimental flu vaccine that uses a protein from the influenza A virus (the nucleoprotein) linked to small pieces of a bird protein. This combination is designed to stimulate a broader immune response that may protect against many flu strains. It is also administered by injection into the muscle.

  • OVX836C2

    is the test product in this study. It mixes the OVX836 vaccine with the three inactivated flu viruses found in GC FLU, creating a single injection that contains both the nucleoprotein component and the standard hemagglutinin proteins from H3N2, H1N1, and influenza B. The goal is to see if this combined vaccine works safely and creates a strong immune response.

  • Vaxigrip

    is a licensed, standard trivalent influenza vaccine that contains inactivated (killed) flu viruses representing two A subtypes and one B strain. It is the reference vaccine used in many flu studies and is given as an intramuscular injection.

What is already known about the treatment

  • Sodium Chloride Intravenous Infusion BP 0.9% w/v Solution for Infusion

    This sterile salt‑water solution is given by injection into the muscle and is used as a placebo in the study. It is a widely available electrolyte product that is routinely used to replace fluids and salts in medical practice. Its main purpose is to provide sodium and chloride ions to keep the body’s fluid balance normal. It belongs to the class of electrolyte solutions.

  • GC FLU

    This vaccine is injected into the muscle as a pre‑filled syringe and contains inactivated influenza virus proteins from three flu strains. It is an approved seasonal flu vaccine that is used to prevent influenza disease. The dead virus proteins stimulate the immune system to make antibodies that block the real virus from causing infection. It is classified as an inactivated viral vaccine.

  • OVX836

    This experimental product is given by intramuscular injection as a clear solution and contains a piece of the influenza A virus protein (nucleoprotein) linked to fragments of a bird protein. It is still being studied in clinical trials and is not yet approved for general use. The protein triggers the body’s immune cells to recognize and attack cells infected with flu virus. It is a recombinant protein subunit vaccine.

  • OVX836C2

    This investigational vaccine is administered by intramuscular injection and combines the OVX836 protein with the same inactivated influenza virus proteins used in GC FLU. It is being tested in the trial and is not yet on the market. The mix aims to teach the immune system to make antibodies against the virus surface (HA) while also training T‑cells to recognize the internal nucleoprotein, giving broader protection. It is a combined protein subunit and inactivated virus vaccine.

  • Vaxigrip suspension injectable en seringue préremplie

    This licensed vaccine is injected into the muscle as a suspension and contains inactivated fragments of three influenza virus strains. It is an approved trivalent flu vaccine used worldwide to prevent seasonal influenza. The dead virus pieces stimulate the body to produce antibodies that block infection by the matching flu viruses. It belongs to the class of inactivated influenza vaccines.

Investigated diseases

Influenza - Influenza is an acute respiratory infection caused by influenza viruses. It usually starts with sudden fever, chills, muscle aches, and a dry cough. Symptoms may progress to sore throat, nasal congestion, and fatigue. In most people the illness resolves within a week, though some experience lingering cough or weakness for several weeks. The virus spreads easily through droplets when an infected person coughs or sneezes. Seasonal outbreaks occur each year as the virus changes over time.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase I/IITrial ID2026-526939-19-00Protocol codeOVX836C2Estimated enrolment250 patientsSponsorOsivax

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