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Study on the Immune Response and Safety of a New Varicella Vaccine (GSKVX000000025896) Compared to Varicella Virus Oka/Merck Strain in Healthy Children Aged 12-15 Months

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

This clinical trial is focused on studying a disease known as , commonly referred to as chickenpox. The study involves testing a new vaccine designed to protect against this disease. The vaccine being tested is called , and it is produced by a company named MSD Sharp & Dohme GmbH. Another vaccine, known as , will also be used in the study for comparison. Additionally, a vaccine with the code name from GlaxoSmithKline Biologicals S.A. will be part of the study.

The purpose of the study is to evaluate the immune response and safety of the new chickenpox vaccine when given to healthy children aged 12 to 15 months. The study will compare the new vaccine with the existing VARIVAX® vaccine to see if it produces a similar immune response. The study will also look at the safety of the vaccines by monitoring any side effects that may occur after vaccination.

Participants in the study will receive either the new vaccine or the VARIVAX® vaccine. The study will last for several months, during which time the children will be monitored for their immune response to the vaccine and any side effects. The study aims to ensure that the new vaccine is safe and effective in preventing chickenpox in young children.

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

    Initial visit and consent

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

    A medical history review and clinical examination will be conducted to confirm the child's health status and eligibility for the study.

  2. Step 2

    Vaccine administration

    The child will receive a dose of the investigational varicella vaccine or the comparator vaccine, Varivax, as a subcutaneous injection. This means the vaccine will be injected under the skin.

    The vaccine is administered as a single dose to healthy children aged 12 to 15 months.

  3. Step 3

    Monitoring and follow-up

    After the vaccine is administered, the child will be monitored for any immediate reactions at the injection site or systemic reactions such as fever, irritability, or loss of appetite.

    Parents or guardians will be required to complete electronic diaries (eDiaries) to record any symptoms or reactions observed in the child from Day 1 to Day 43.

  4. Step 4

    Follow-up visits

    The child will return for follow-up visits to assess the immune response to the vaccine. Blood samples may be taken to measure the concentration of antibodies against the varicella zoster virus.

    The primary assessment of the immune response will occur on Day 43 after the vaccine administration.

  5. Step 5

    Long-term safety monitoring

    The study will continue to monitor the child for any adverse events or serious adverse events up to Day 181. This includes any medical attention required due to symptoms or illnesses.

    Parents or guardians will be informed of any significant findings related to the child's health during this period.

Who can join the trial?

5 criteria

  • The participant's parent(s) or legally acceptable representative(s) must be able to follow the study requirements, like filling out electronic diaries and attending follow-up visits.
  • 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 done.
  • The participant must be healthy as determined by their medical history and a physical examination before joining the study.
  • The participant must be a male or female between 12 to 15 months of age, which means from their first birthday until the day before they turn 16 months old, at the time of receiving the study interventions.
  • 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?

7 criteria

  • People who have had a recent infection with the **Varicella** virus, which is the virus that causes chickenpox, cannot participate.
  • Individuals who have received any other **Varicella** vaccine recently are not eligible.
  • Participants with a weakened immune system, which means their body has a harder time fighting infections, are excluded.
  • Pregnant women or those planning to become pregnant during the study period cannot take part.
  • Anyone with a history of severe allergic reactions to vaccines or any component of the study vaccine is not allowed to join.
  • People currently participating in another clinical trial are not eligible.
  • Individuals with any other significant health issues that the study doctors believe could interfere with the study results are excluded.
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Investigated drugs

  • VNS vaccine

    is an investigational vaccine being tested to protect against the varicella zoster virus, which causes chickenpox. The study aims to see if different batches of this vaccine produce a consistent immune response in children aged 12 to 15 months. The vaccine is given as a first dose to help the body build protection against the virus.

  • Varivax

    is an existing vaccine used to prevent chickenpox. In this study, it serves as a comparison to the investigational VNS vaccine. By comparing the immune response and safety of Varivax with the new vaccine, researchers can determine if the new vaccine is as effective and safe as the established one. Varivax is also given as a first dose to healthy children aged 12 to 15 months.

What is already known about the treatment

VNS vaccine – The VNS vaccine is administered as an injection to healthy children aged 12 to 15 months to protect against chickenpox, also known as varicella. Currently, this vaccine is being studied in clinical trials to ensure its effectiveness and safety compared to an existing vaccine called Varivax. The main purpose of the VNS vaccine is to help the body build immunity against the varicella-zoster virus, which causes chickenpox. It works by stimulating the immune system to produce antibodies that can recognize and fight the virus. This vaccine is classified as a live attenuated vaccine, meaning it contains a weakened form of the virus that cannot cause the disease but can still prompt an immune response.

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 from red spots to fluid-filled blisters, and eventually to scabs. The rash usually starts on the face, chest, and back before spreading to the rest of the body. The disease is most common in children, but it can affect individuals of any age. After the initial infection, the virus can remain dormant in the body and may reactivate later in life as shingles. The progression of the rash and symptoms usually occurs over a period of about one to two weeks.
Trial detailsLast updated 7 Oct 2026
Age0-17PhasePhase IIITrial ID2024-515869-33-00Protocol code213998 (VNS 20-002)Estimated enrolment1 840 patientsSponsorGlaxoSmithKline Biologicals

sourced from the EU Clinical Trials Register and site verification

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