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Study of the safety and immune response of gskvx000000077430 drug combination versus standard influenza vaccine in adults 18‑64 years

Verified siteRegistered drugNo placebo
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What is this trial about?

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

The study focuses on influenza, a viral infection that causes fever, cough, and body aches. The investigational product is a mRNA-based seasonal influenza vaccine that is given as a single injection into the muscle. For comparison, two standard flu vaccines, Efluelda TIV‑HD and another trivalent influenza vaccine, are also used.

The purpose of the study is to determine whether the new vaccine produces an immune response that is not worse than the response seen with the existing vaccines and to assess its safety. Immunogenicity, which means the ability of the vaccine to stimulate the body’s defenses, will be measured by looking at antibodies against the virus’s surface proteins called HA and NA. These antibodies are measured with a test called HI (hemagglutination inhibition). Reactogenicity, or the short‑term side effects such as soreness at the injection site, fever, or muscle aches, will be recorded for a week after vaccination, and any other health problems will be followed for several months. Some participants may receive a placebo instead of the active vaccine.

Participants will receive one dose of the assigned product, stay for a short observation period, and then return for brief visits or phone calls at about one week, one month, and up to six months to collect safety information and blood samples for antibody testing. The study is designed to be double‑blind, meaning neither the participants nor the staff who assess outcomes will know which product was given, to keep the results unbiased.

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

    Vaccination (day 0)

    On the day you join the study you receive a single dose of the assigned vaccine. the dose is 0.5 ml and is given by an intramuscular injection into the upper arm. the injection may be the investigational mRNA influenza vaccine or one of the approved comparator influenza vaccines. after the injection you stay in the clinic for about 30 minutes for observation.

  2. Step 2

    Daily symptom recording (days 1‑7)

    For the first seven days you keep a diary of any symptoms. record injection‑site reactions such as pain, redness, or swelling, and systemic symptoms such as fever, headache, or muscle aches. the diary helps the study team assess how your body reacts to the vaccine.

  3. Step 3

    Safety check (day 7)

    Around day 7 you have a brief contact with study staff, either in person or by phone. during this contact you discuss any symptoms you recorded and report any adverse events that were not captured in the diary.

  4. Step 4

    Blood sample for immune response (day 29)

    Approximately four weeks after vaccination you return to the clinic for a blood draw. the sample is used to measure your immune response to the vaccine. no additional vaccine dose is given at this visit.

  5. Step 5

    Ongoing safety monitoring (up to 6 months)

    For up to six months after the injection you continue to report any serious health problems or events that might be related to the study. this may involve periodic phone calls or additional clinic visits, but no further vaccine doses are administered.

Who can join the trial?

4 criteria

  • Be able to follow the study rules, such as filling out a electronic diary (an app or computer program for recording information), returning for follow‑up visits, and using a phone or other electronic communication, either on your own or with help from a caregiver.
  • Provide written or digitally recorded informed consent (a signed agreement that you understand the study and agree to take part) before any study procedures are done.
  • Be a healthy person or have a medical condition that is medically stable. This means any long‑lasting illnesses (called chronic medical conditions, such as diabetes, heart disease, lung problems, kidney or liver disease, brain or blood disorders) must not have needed a major change in treatment or a hospital stay for worsening in the past three months.
  • Be between 18 and 64 years old (including 18 and 64) at the time you receive the study vaccine.

Who cannot join the trial?

6 criteria

  • People who have a confirmed or suspected immunosuppressive (weakening the immune system) or immunodeficient (insufficient immune function) condition are not allowed, unless they have HIV that has been stable on medication for at least 6 months, with a CD4 count of 200 or higher and an undetectable viral load.
  • Anyone who has ever had myocarditis (inflammation of the heart muscle) or pericarditis (inflammation of the lining around the heart) that was linked to an mRNA vaccine cannot take part.
  • People with acute (sudden) or unstable chronic illnesses such as serious lung, heart, liver, hormone (metabolic/endocrine), kidney, or psychiatric (mental health) problems are excluded.
  • If you received an influenza vaccine within the past 180 days (about 6 months) or plan to receive one before a certain study visit, you cannot join.
  • If you have had a lab‑confirmed flu infection within the past 180 days, you are not eligible.
  • Anyone taking immune‑modifying drugs for more than 14 consecutive days, or planning to start long‑acting immune‑modifying treatments during the study, is excluded. This includes taking systemic corticosteroids (like prednisone) at a dose of 20 mg per day or higher for more than 14 days within the 90 days before the study. Inhaled, joint‑injection, or skin‑applied steroids are allowed. It also includes drugs such as TNF inhibitors, monoclonal antibodies, or cancer‑related medications.
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Investigated drugs

  • Efluelda TIV‑HD

    is a trivalent influenza vaccine that contains three inactivated flu viruses (one type B and two type A strains). It is given as a small injection into the muscle. In this study it is used as a standard vaccine to compare the new vaccine against, helping researchers see how well the new product works and how safe it is.

  • Alpharix

    is another trivalent influenza vaccine that also includes three inactivated flu viruses (one type B and two type A strains). Like the other comparator, it is administered by injection into the muscle. It serves as an additional reference vaccine in the trial so the new vaccine’s performance can be measured against more than one established flu shot.

  • GSKVX000000077430, GSKVX000000077508, GSKVX000000077506, GSKVX000000077510, GSKVX000000077509, GSKVX000000077507

    are code‑named experimental products that together form an mRNA‑based seasonal influenza vaccine being tested in the trial. The vaccine uses messenger RNA technology to teach the body’s cells to produce flu‑virus proteins, triggering an immune response. It is delivered as a dispersion for injection into the muscle, and the study is evaluating whether it produces a strong immune response and is safe compared with the standard flu vaccines.

What is already known about the treatment

  • Efluelda TIV‑HD

    This vaccine is given as a 0.5 ml intramuscular injection of a suspension that contains inactivated trivalent influenza virus strains. It is an approved, commercially available flu vaccine that is used each year to prevent influenza infection. The vaccine works by presenting the body with viral surface proteins (hemagglutinin and neuraminidase) so the immune system can learn to recognize and fight the real virus. It is classified as an inactivated (purified antigen) influenza vaccine.

  • Alpharix

    Alpharix is administered as a 0.5 ml intramuscular injection of a suspension containing three inactivated influenza virus strains. It is a licensed seasonal flu vaccine used to protect people from influenza illness. The vaccine contains split viral particles that display hemagglutinin and neuraminidase, allowing the immune system to develop antibodies that block infection. It belongs to the pharmacological class of inactivated (purified antigen) influenza vaccines.

  • GSKVX vaccine (investigational mRNA influenza vaccine)

    The study product is delivered as a 0.5 ml intramuscular injection of a dispersion that carries messenger RNA encoding influenza hemagglutinin proteins. It is an experimental vaccine currently in phase 3 clinical testing and not yet approved for general use. The mRNA enters muscle cells, which then produce the viral hemagglutinin protein, prompting the body to mount an immune response without exposure to the actual virus. This product is classified as an mRNA‑based viral vaccine.

Investigated diseases

Influenza - Influenza is an acute respiratory infection caused by influenza viruses that spread through respiratory droplets. After an incubation period of one to four days, people typically develop sudden fever, chills, cough, sore throat, and muscle aches. The illness usually begins in the upper airway and can spread to the lower respiratory tract, leading to bronchitis or pneumonia in some cases. Symptoms often peak within two to three days and then gradually improve over a week. The disease can recur each season as the virus changes its surface proteins.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2026-526925-17-00Protocol code218132Estimated enrolment3 000 patientsSponsorGlaxoSmithKline Biologicals

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