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SARS‑CoV‑2 spike protein vaccine and drug combination study in adults 60 years and older with COVID‑19 and influenza

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What is this trial about?

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

The study involves adults aged 60 years and older who are at risk for COVID-19 and Influenza. A new combination vaccine that contains a recombinant spike (a lab‑made piece of the virus that teaches the immune system) from the virus that causes COVID‑19 and a high‑dose inactivated influenza vaccine (a flu shot with a larger amount of killed virus to create a stronger response) with a Matrix‑M adjuvant (a substance that helps the immune system respond better) is being tested. The combination will be compared with the individual vaccines, a standard high‑dose flu shot known as FLUZONE‑HD, a COVID‑19 shot called Nuvaxovid, and a simple saline solution used as a placebo. The purpose of the study is to see whether the combined product produces a similar immune response and safety profile as the separate vaccines.

Participants will receive a single intramuscular injection according to the group they are assigned to and will stay for a short observation period after the shot. Over the next several weeks they will return for a few clinic visits where blood samples are taken to check the level of antibody (proteins that help protect against infection) and where any injection‑site or overall reactions are recorded. Participants will be asked to note any symptoms such as pain, redness, fever, or fatigue for about a week after vaccination, and any health events that occur later will be reported to the study team. The overall time in the study lasts a few months, allowing researchers to evaluate short‑term safety and the body’s immune response.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Receive study injection (day 0)

    After enrollment you will be assigned to one of the study groups. you will receive a single intramuscular injection in the upper arm. the volume depends on the group: 1 milliliter for the combination vaccine, 0.5 milliliter for the influenza vaccine, 0.5 milliliter for the covid-19 vaccine, or a small amount of 0.9% saline (placebo). the injection contains either the combined covid-19 spike protein and high‑dose influenza antigens with matrix‑m adjuvant, only the influenza antigens, only the covid‑19 spike protein, or no active medicine.

  2. Step 2

    Observation for immediate reactions

    After the injection you will stay in the clinic for about thirty minutes while staff watch for any immediate adverse events, such as an allergic reaction. this short observation helps ensure your safety right after vaccination.

  3. Step 3

    Daily monitoring for eight days

    For the next eight days, including the day of vaccination, you will record any injection site reactions (such as pain, redness, or swelling at the injection spot) and any systemic reactions (such as fever, headache, or muscle aches). a diary or questionnaire will be provided for you to note these symptoms each day.

  4. Step 4

    Day 8 follow‑up visit

    On day eight you will return to the clinic (or have a phone call) to report the symptoms you recorded and to discuss any other health problems that may have occurred. a brief physical check may be performed.

  5. Step 5

    Blood draw for antibody testing (day 29)

    On day twenty‑nine you will come back for a small blood sample. this blood draw is used to perform an antibody test that measures the level of immune proteins against the three influenza strains and against covid‑19 variants. no additional injection is given at this visit.

  6. Step 6

    Ongoing safety monitoring

    Throughout the remainder of the study you will be asked to report any new health events, especially those that could be related to the study product. this includes serious health problems, visits to a doctor, or any events that the study defines as special interest. reporting can be done by phone or during scheduled clinic visits until the study ends.

Who can join the trial?

7 criteria

  • Be at least 60 years old on the day you join the study.
  • Be able to go to all scheduled study visits and follow the study instructions.
  • Be able to receive an injection in the deltoid muscle (the muscle at the top of each upper arm) of both arms.
  • Have completed the full initial COVID‑19 vaccine series and received at least one booster dose of a locally approved COVID‑19 vaccine.
  • Sign and date the informed consent form, which shows you understand the study and agree to take part.
  • Be generally healthy or have a medical condition that is stable, as confirmed by a doctor’s review of your medical history and a physical exam.
  • Not be able to become pregnant, meaning you are either post‑menopausal for at least one year or have had a surgical procedure that makes you sterile.

Who cannot join the trial?

16 criteria

  • Known or suspected weak immune system (called immunodeficiency), or having taken medicines that suppress the immune system in the past 6 months, or long‑term use of steroids (a type of anti‑inflammatory medication).
  • Past diagnosis of myocarditis (inflammation of the heart muscle), pericarditis (inflammation of the lining around the heart), or myopericarditis (both together).
  • Any vaccine given within 4 weeks before or 4 weeks after the study injection.
  • Having received a flu (influenza) vaccine, whether a regular or experimental one, in the 6 months before the study, or having had flu illness in that time.
  • Having received a COVID‑19 vaccine, whether a regular or experimental one, in the 6 months before the study, or having had COVID‑19 infection in that time.
  • Having a blood transfusion or blood‑derived products (including immunoglobulins, which are antibodies taken from donated blood) in the past 3 months.
  • Being confined by a legal or court order, being in an emergency situation, or being hospitalized against one’s will.
  • Being a study investigator, a study‑center employee, or an immediate family member (parent, spouse, child) of someone directly involved in the study.
  • Known severe allergy (systemic hypersensitivity) to any part of the study vaccine, or a past life‑threatening reaction to similar products.
  • Self‑reported low platelet count (thrombocytopenia) that makes an intramuscular injection unsafe, according to the doctor’s judgment.
  • Having a bleeding disorder or having taken blood‑thinning medicines (anticoagulants) in the 3 weeks before joining, which could make an intramuscular injection unsafe, according to the doctor’s judgment.
  • Having a chronic (long‑term) illness that the doctor believes could interfere with completing the study.
  • Having a moderate or severe acute (sudden) illness or infection, or a fever of 38 °C (100.4 °F) or higher on the day of the study injection; participation is allowed only after the illness or fever has resolved.
  • Alcohol, prescription drug, or other substance abuse that the doctor thinks could interfere with the study.
  • History of a serious adverse reaction to any flu or COVID‑19 vaccine, as judged by the doctor.
  • Personal or family history of Guillain‑Barré syndrome, a rare condition that can cause muscle weakness.
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Investigated drugs

  • Efluelda

    is a flu vaccine that contains three inactivated influenza viruses: one type B strain and two type A strains (H1N1 and H3N2). It is given as an intramuscular injection. In this study it is used as a standard flu vaccine to compare how well the new combination vaccine protects against the flu.

  • Nuvaxovid

    is a COVID‑19 vaccine made from a piece of the virus’s spike protein that is produced in insect cells. It also contains an adjuvant to help the immune system respond. The vaccine is injected into the muscle. In the trial it serves as the standard COVID‑19 vaccine to compare the immune response of the combination product.

  • Fluzone HD + NVXC19 combination vaccine

    combines a high‑dose inactivated flu vaccine (the same type used in Fluzone HD) with a recombinant spike protein COVID‑19 vaccine (NVXC19) that includes a Matrix‑M adjuvant. Both components are mixed together in a single syringe and given as an intramuscular injection. This test vaccine is being evaluated to see if it can safely protect older adults against both influenza and COVID‑19 in one shot.

What is already known about the treatment

  • 0.9% NaCl Solution

    This sterile salt water is given by injection, usually into a vein, and is used in the trial as a placebo. It is a standard medical product that is widely available in hospitals and has no active drug effect. The solution simply provides an isotonic fluid to keep the body balanced and is classified as an isotonic crystalloid solution.

  • Efluelda

    The vaccine is a suspension that is injected into the muscle and contains three inactivated influenza virus strains. It is an approved flu vaccine used to protect adults from seasonal influenza infections. The inactivated viruses stimulate the body to make antibodies that recognize the flu virus, and it belongs to the class of split‑virion, inactivated influenza vaccines.

  • Nuvaxovid

    This dispersion is given as an intramuscular injection and contains a lab‑made piece of the SARS‑CoV‑2 spike protein made in insect cells, plus an adjuvant to boost the response. It is an authorized COVID‑19 vaccine that helps the immune system produce protective antibodies against the virus. By presenting the spike protein, it teaches the body to recognize and fight the real virus, and it is classified as a recombinant protein COVID‑19 vaccine with adjuvant.

  • FLUZONE‑HD + Baculo adj COVID19 (NVXC19)

    The combination product is a suspension injected into the muscle that mixes a high‑dose inactivated flu virus with a recombinant SARS‑CoV‑2 spike protein and a Matrix‑M adjuvant. It is still under investigation in this trial and is not yet an approved medication. It aims to protect older adults from both influenza and COVID‑19 by triggering separate immune responses to the flu antigens and the spike protein, and it is classified as a combination vaccine (inactivated influenza + recombinant protein COVID‑19 vaccine).

Investigated diseases

  • COVID-19

    COVID-19 is an infection caused by the SARS‑CoV‑2 virus that mainly involves the respiratory tract. It usually begins with symptoms such as fever, cough, and loss of smell or taste. Over several days the illness can spread to the lower airways, leading to shortness of breath or chest discomfort. Some people experience fatigue, muscle aches, or mild gastrointestinal upset as the disease continues. In most cases the symptoms improve within two weeks, although a few individuals notice lingering tiredness for a longer period.

  • Influenza

    Influenza is an acute respiratory illness caused by influenza viruses that circulate each year. The infection starts abruptly with fever, chills, headache, and body aches. A cough and sore throat often develop, and the symptoms typically peak within three to five days. Most people feel better after about a week, although the cough and fatigue may persist for several more days. The illness usually resolves without lasting effects in healthy individuals.

Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2026-526221-18-00Protocol codeVBT00004Estimated enrolment7 535 patientsSponsorSanofi Vaccines US Inc.

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