Skip to content
Clinical Trials – home

Rare diseases

Investigational molecules

Locations

Our offerNewsroom

Not yet recruiting

Study on the Immune Response and Safety of a Second Dose of Investigational Varicella Vaccine (GSKVX000000025896) Compared to Varicella Virus Oka/Merck Strain in Healthy Children

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

This clinical trial is focused on studying the immune response and safety of a second dose of an investigational vaccine for chickenpox, also known as varicella. The study involves healthy children who have already received a first dose of the vaccine between the ages of 12 to 15 months. The investigational vaccine is being compared to an existing vaccine called VARIVAX®, which contains a live, weakened form of the varicella virus. The investigational vaccine is identified by the code name GSKVx000000061721.

The purpose of the study is to evaluate how well the investigational vaccine works in generating an immune response compared to the existing vaccine. The study will involve giving a second dose of either the investigational vaccine or the existing vaccine to the children three months after their first dose. The vaccines are given as an injection under the skin, known as a subcutaneous injection. The study will monitor the children's immune response to the varicella zoster virus and any side effects that may occur after receiving the second dose.

Throughout the study, researchers will observe the children for any reactions at the injection site and any general symptoms, such as fever. The study will also track any unexpected health issues that may arise. The goal is to ensure that the investigational vaccine is as effective and safe as the existing vaccine in protecting against chickenpox. The study is expected to continue until the end of 2026.

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

    Joining the study

    Upon joining the study, the participant's parent or legally acceptable representative must provide written or witnessed consent. This consent is necessary before any study-specific procedures can begin.

    The participant must be healthy, as determined by a medical history review and clinical examination.

  2. Step 2

    First dose administration

    The first dose of the investigational varicella vaccine is administered to the participant. This vaccine is given as a suspension for injection under the skin, known as a subcutaneous injection.

    The participant must be between 12 to 15 months of age at the time of this first dose.

  3. Step 3

    Monitoring after first dose

    After the first dose, the participant is monitored for any solicited administration site events from Day 1 to Day 4.

    Monitoring for solicited systemic events, such as fever, occurs from Day 1 to Day 22.

    Any unsolicited adverse events are recorded from Day 1 to Day 43.

  4. Step 4

    Second dose administration

    Three months after the first dose, the second dose of the investigational varicella vaccine is administered. This is also given as a suspension for injection under the skin.

    The second dose is crucial for evaluating the immune response and safety of the vaccine.

  5. Step 5

    Monitoring after second dose

    Following the second dose, monitoring for solicited administration site events occurs from Day 91 to Day 94.

    Monitoring for solicited systemic events, including fever, takes place from Day 91 to Day 112.

    Any unsolicited adverse events are recorded from Day 91 to Day 133.

  6. Step 6

    Final evaluation

    The primary evaluation of the immune response is conducted 43 days after the second dose, on Day 133.

    The study continues to monitor for any medically attended adverse events and serious adverse events until the end of the study on Day 271.

Who can join the trial?

5 criteria

  • The participant's parent(s) or legally acceptable representative(s) must be able and willing to follow the study requirements, according to the study investigator.
  • Written or witnessed/thumb-printed informed consent must be obtained from the participant's parent(s) or legally acceptable representative(s) before any study-specific procedures are performed.
  • The participant must be healthy, as determined by medical history and a clinical examination before joining the study.
  • The participant must be a male or female between 12 to 15 months of age. This means from the day they turn 1 year old until the day before they turn 16 months old, at the time of the first study intervention.
  • For children in countries where the Pneumococcal Conjugate Vaccine (PCV) is recommended at 12 to 15 months of age as part of the national immunization schedule and provided as part of the study interventions: The participant must have previously received the primary series of PCV in the first year of life, with the last dose given at least 60 days before entering the study.

Who cannot join the trial?

9 criteria

  • Having a current or past infection with Varicella (also known as chickenpox).
  • Receiving any other vaccines within 4 weeks before the first dose of the study vaccine.
  • Having a known allergy to any component of the study vaccine.
  • Having a weakened immune system, which means your body has a harder time fighting infections.
  • Being pregnant or planning to become pregnant during the study period.
  • Breastfeeding during the study period.
  • Participating in another clinical trial at the same time.
  • Having a history of severe reactions to vaccines in the past.
  • Having any other medical condition that the study doctors think might make it unsafe for you to 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.

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

  • Investigational Varicella Vaccine (VNS)

    is a new vaccine being tested to see how well it works in protecting against chickenpox. Chickenpox is a common childhood illness caused by the varicella-zoster virus, which can cause an itchy rash and fever. This vaccine is given to children to help their bodies build up defenses against the virus, so they are less likely to get sick if they are exposed to it. In this study, the vaccine is given as a second dose to see if it helps improve the immune response compared to the standard vaccine.

  • Varivax

    is an existing vaccine that is already used to protect children against chickenpox. It works by helping the body develop immunity to the varicella-zoster virus, which causes chickenpox. In this study, Varivax is used as a comparison to the new investigational vaccine to see if the new vaccine is as effective or better in boosting the immune system's response to the virus when given as a second dose.

What is already known about the treatment

Investigational Varicella Vaccine (VNS) – This vaccine is administered as an injection to healthy children, typically given as a second dose three months after the first dose, which is administered at 12 to 15 months of age. It is currently being studied in clinical trials to assess its effectiveness and safety compared to an existing varicella vaccine, Varivax. The main purpose of this vaccine is to protect against varicella, commonly known as chickenpox. It works by stimulating the immune system to produce antibodies against the varicella-zoster virus, which causes chickenpox. This investigational vaccine is classified as a live attenuated vaccine, meaning it contains a weakened form of the virus to safely build immunity without causing the disease.

Investigated diseases

Varicella – Varicella, commonly known as chickenpox, is a highly contagious viral infection caused by the varicella-zoster virus. It typically begins with a fever, fatigue, and a characteristic itchy rash that progresses to fluid-filled blisters. These blisters eventually crust over and heal. The rash usually starts on the face, chest, and back before spreading to the rest of the body. The disease is more common in children, but it can occur at any age. After the initial infection, the virus can remain dormant in the body and may reactivate later in life as shingles.
Trial detailsLast updated 7 Oct 2026
Age0-17PhasePhase IIITrial ID2024-516635-27-00Protocol code214002 (VNS 20-004)Estimated enrolment600 patientsSponsorGlaxoSmithKline Biologicals

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.