Skip to content
Clinical Trials – home

Rare diseases

Investigational molecules

Locations

Our offerNewsroom

Not yet recruiting

Effectiveness of mCOMBRIAX vaccine compared with high‑dose influenza vaccine and mRNA‑1273 in adults ≥65 years for prevention of influenza and COVID‑19

Verified siteRegistered drugNo placebo
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

What is this trial about?

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

The trial focuses on two common viral illnesses that affect older adults: Influenza infection and SARS‑CoV‑2 infection. It evaluates a new vaccine called mCombriax, which combines protection against both flu and COVID‑19 in a single injection. The vaccine uses messenger RNA (mRNA) to teach the body to recognize pieces of the flu viruses and the spike protein of the coronavirus. The study compares this combined vaccine with the usual practice of giving a high‑dose flu shot (Efluelda) and a COVID‑19 shot (Spikevax) at the same visit.

The purpose of the study is to determine whether the combined vaccine prevents doctor visits or hospital stays caused by flu or COVID‑19 as well as, or better than, the two separate shots. Participants aged 65 years or older will receive either the combined vaccine or the two separate vaccines on the same day and will be observed for several months. Any illness that leads to a medical appointment, emergency care, or hospitalization will be recorded to assess the vaccine’s effectiveness.

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

    Randomization and assignment

    After joining the trial you will be placed into one of two groups by a random process. one group receives the test vaccine mcombrax, the other group receives two standard vaccines given on the same day.

  2. Step 2

    Vaccine administration

    If you are assigned to the test group, a single intramuscular injection of mcombrax will be given. the injection contains a dose of 1 mg (milligram) of the vaccine formulation.

    If you are assigned to the comparator group, you will receive two intramuscular injections on the same visit: one injection of efluelda (influenza vaccine) with a dose of 1 µg (microgram) and one injection of spikevax (covid‑19 vaccine) also with a dose of 1 µg. both injections are given into the muscle.

  3. Step 3

    Immediate post‑vaccination observation

    After the injection(s) you will be asked to stay at the study site for about 15 to 30 minutes so that staff can watch for any immediate reactions.

  4. Step 4

    Ongoing follow‑up for health events

    Throughout the study period, which may last up to three years, you will continue your normal daily activities. if you experience symptoms of influenza or covid‑19, or if you need medical care or are hospitalized, you should seek care as usual and the study team will record those events.

    The trial will track two main outcomes: (1) any medically attended influenza or covid‑19 infection, and (2) any influenza or covid‑19 related hospitalization.

  5. Step 5

    Final study visit

    At the end of the study period, a final visit will be scheduled to complete any remaining study procedures and to close your participation.

Who can join the trial?

3 criteria

  • Age: You must be 65 years old or older at the time you receive the vaccine.
  • Language ability: You need to be able to read and understand the study information in English, or if you live in Denmark, in Danish, or if you live in Spain, in Spanish or Galician.
  • Informed consent: You must sign and date a consent form that shows you understand the study and agree to take part.
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.

We usually reply within a few days

Verified sites

All sites with verified contact details – recruitment status may not be available; ask directly

Trial locations

Where you can join this trial

Countries are shaded by recruitment status. Click a recruiting country to ask about joining there.

Not yet recruiting
Not finding your country?

Not sure what to do next?

Joining a clinical trial can seem overwhelming. We guide you step by step, so you know exactly what to expect and how we support you through the process.

See the full process and FAQ

Investigated drugs

  • Efluelda Tetra

    is a high‑dose, quadrivalent influenza vaccine given by injection into the muscle. It contains inactivated (killed) flu viruses that represent the most common strains expected each season. The vaccine works by teaching the immune system to recognize these flu viruses, helping to prevent influenza infection in older adults.

  • Spikevax

    is a COVID‑19 mRNA vaccine (also known as Moderna’s Spikevax) administered as an intramuscular injection. It contains messenger RNA that provides the body’s cells with the instructions to make a harmless piece of the coronavirus spike protein. This triggers an immune response that protects against COVID‑19 infection.

  • mCOMBRIAX

    is a combined vaccine that includes mRNA components for both influenza and COVID‑19. The influenza part targets the H1N1, H3N2, and B strains of flu, while the COVID‑19 part encodes key portions of the SARS‑CoV‑2 spike protein (specifically the XBB.1.5 variant). Given by injection, this single vaccine is designed to stimulate the immune system to protect against both flu and COVID‑19 in one shot.

What is already known about the treatment

  • Efluelda

    The vaccine is given as an intramuscular injection of a suspension that contains inactivated influenza viruses from several strains. It is an approved high‑dose influenza vaccine that is widely used in clinical practice and listed in medical literature. It is intended to protect adults from seasonal influenza infection. The inactivated virus particles stimulate the immune system to produce antibodies, classifying it as a purified antigen influenza vaccine (ATC J07BB02).

  • Spikevax

    This product is administered by a single intramuscular injection of a sterile dispersion containing messenger RNA that codes for the SARS‑CoV‑2 spike protein. Spikevax is an authorized COVID‑19 vaccine that has been approved in many countries and is described in the scientific literature. It is used to prevent COVID‑19 infection and its severe outcomes. The mRNA enters cells, directs them to make a harmless piece of the spike protein, and the resulting protein triggers an immune response, making it an mRNA COVID‑19 vaccine (ATC J07BN01).

  • mCOMBRIAX

    The vaccine is delivered as a single intramuscular injection of a dispersion that carries four different mRNA strands, each encoding either an influenza hemagglutinin protein (H1N1, H3N2, B) or the SARS‑CoV‑2 spike protein (XBB.1.5). It is currently an investigational product being studied in clinical trials and is not yet approved for general use. It aims to protect older adults from both influenza and COVID‑19 infections. The mRNA molecules are taken up by cells, which then produce the viral proteins that train the immune system to recognize and fight the real viruses, placing it in the experimental combined mRNA vaccine category.

Investigated diseases

  • COVID-19

    COVID-19 is a viral infection caused by SARS‑CoV‑2 that mainly involves the respiratory system. It often starts with fever, cough, and fatigue and can spread to the lower airways. The illness may progress from mild upper‑respiratory symptoms to more extensive lung involvement, increasing breathing difficulty. Some individuals also experience muscle aches, headache, or loss of taste and smell. Symptoms usually peak within the first week and then begin to improve.

  • Influenza

    Influenza is an acute respiratory infection caused by influenza viruses, most frequently types A and B. It begins suddenly with fever, chills, headache, and muscle aches, followed by cough and sore throat. The virus moves through the airways and can spread from the upper to the lower respiratory tract. Symptoms typically worsen over two to three days and then gradually resolve over about a week. Occasionally, a lingering cough or fatigue may persist after the acute phase.

Trial detailsLast updated 7 Oct 2026
Age65+ yearsPhasePhase IIITrial ID2026-526720-49-00Protocol codeDAN-COMBOEstimated enrolment410 000 patientsSponsorGentofte Hospital

sourced from the EU Clinical Trials Register and site verification

Want to learn more about this trial or check if you can participate?

Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.