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Study of mRNA-based seasonal influenza vaccine combinations compared to standard influenza vaccines in adults aged 18 and older

2 1 1 1

What is this study about?

This clinical trial aims to evaluate a new mRNA-based seasonal influenza vaccine in adults. The study focuses on testing different versions of an experimental vaccine against influenza, commonly known as the flu. The vaccines will be given as injections into the muscle.

The study will test several different formulations of the vaccine, including versions containing various influenza virus strains. Some participants will receive the experimental mRNA vaccine candidates, while others will receive currently available flu vaccines for comparison. The study will monitor how well the immune system responds to the vaccines and track their safety.

Participants will receive a single dose of 0.5 milliliters of vaccine and will be monitored for 6 months afterward. During this time, researchers will check for immune responses through blood tests and record any side effects that occur. The study will look at both expected injection site reactions and any unexpected health events that might happen after vaccination.

1 Initial visit and vaccination

On Day 1, you will receive a single intramuscular injection of the study flu vaccine.

Before vaccination, a blood sample will be taken and laboratory tests will be performed.

You will need to stay at the study site for observation after receiving the vaccine.

2 Early follow-up visits

You will need to visit the study site on Day 3 and Day 8 for blood tests and safety monitoring.

During the first 7 days after vaccination, you will need to record any injection site reactions (such as pain or redness) or general symptoms in an electronic diary.

3 Main follow-up visit

On Day 29, you will need to visit the study site for blood tests to measure your immune response to the vaccine.

The study team will review any health changes you experienced since the vaccination.

4 Extended monitoring period

For 6 months after vaccination, any significant medical events will need to be reported.

The study will monitor for any serious health events or specific medical conditions of interest during this period.

5 Final assessment

The study will conclude 6 months after your vaccination.

This will include a final review of your health status and any medical events that occurred during the study period.

Who Can Join the Study?

  • Must be able to follow study requirements independently or with caregiver help, including completing electronic diaries and attending study visits
  • Must provide written consent (on paper or digitally) before any study procedures begin
  • Must be at least 18 years old at screening
  • Must be healthy or have stable medical conditions that haven’t required major treatment changes or hospital stays in the past 3 months
  • For women who cannot become pregnant: can participate without additional requirements
  • For women who can become pregnant must:
    • Use effective birth control for at least 4 weeks before the study
    • Have a negative pregnancy test within 24 hours before starting
    • Continue using birth control for 8 weeks after receiving study treatment
  • Must have a body mass index (BMI) between 18 and 33 kg/m² (BMI is a measure of body fat based on height and weight)

Who Cannot Join the Study?

  • History of severe allergic reactions to any vaccine component or life-threatening allergies
  • Previous vaccination against influenza within the last 6 months
  • Current participation in another clinical trial or within 30 days before this study
  • Pregnancy or breastfeeding
  • Any immunodeficiency condition (weakened immune system due to disease or medication)
  • Acute illness or fever (temperature above 38°C/100.4°F) at the time of vaccination
  • Receipt of immunoglobulins (antibody treatments) or blood products within 3 months before the study
  • History of Guillain-Barré syndrome (a rare disorder where the immune system attacks the nerves)
  • Chronic medical conditions that are not well controlled
  • Use of medications that affect the immune system
  • History of severe reactions to previous influenza vaccines
  • Any condition that, in the opinion of the investigator, might interfere with the study evaluations

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

No sites found in this category

Other Sites

Site Name City Country Status
Universitair Ziekenhuis Gent Gent Belgium
Utegdwdsiw Or Awvypah Edegem Belgium

Want to learn more about this study or check if you can participate? Contact us.

Trial status

Country Status Recruitment Start
Belgium Belgium
Not recruiting
09.10.2025

Trial locations

Investigated drugs:

Based on the provided source data, this appears to be a clinical trial studying mRNA-based influenza vaccines, but specific medication names are not provided in the source data. Without detailed information about the specific medications or interventions used in the trial, I cannot provide accurate descriptions of the medications involved.

What we can determine is that the trial involved:

mRNA-based seasonal influenza vaccine – This is a new type of vaccine that uses messenger RNA technology to help protect against multiple strains of seasonal influenza (flu). Unlike traditional flu vaccines, this type uses genetic material (mRNA) to instruct cells to produce proteins that trigger an immune response against the influenza virus.

Investigated diseases:

Influenza – A highly contagious viral respiratory infection that affects the nose, throat, and sometimes the lungs. The virus spreads through tiny droplets when infected people cough, sneeze, or talk. Symptoms typically appear suddenly and include fever, chills, muscle aches, fatigue, headache, dry cough, and runny nose. The illness usually develops within 1-4 days after exposure to the virus. The intensity of symptoms can vary from mild to severe, with most people recovering within a week to ten days.

Trial ID:
2025-522278-35-00
Protocol code:
300356
Trial Phase:
Therapeutic exploratory (Phase II)

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