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Efficacy, Safety, and Immunogenicity of mRNA-1647 Vaccine in Preventing Primary Cytomegalovirus Infection in CMV-Seronegative Females Aged 16-40

Fast replyRegistered 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 the prevention of Cytomegalovirus (CMV) infection using a vaccine called mRNA-1647. CMV is a common virus that can cause health problems in some people, especially those with weakened immune systems or pregnant women. The trial aims to evaluate how well the vaccine works, its safety, and how the body responds to it. The vaccine is given as a solution for injection and is designed to help the body build immunity against CMV.

The study involves healthy participants aged 16 to 40 years. Participants will receive the mRNA-1647 vaccine or a placebo through a series of three injections. The trial will monitor participants over a period of time to see if the vaccine can prevent CMV infection and to check for any side effects. The study will also involve the use of Sodium Chloride 0.9%, which is a common solution used in medical settings, as part of the injection process.

The main goal of the study is to demonstrate the effectiveness of the mRNA-1647 vaccine in preventing CMV infection in participants who have not been previously exposed to the virus. The trial will also assess the safety of the vaccine and how well it is tolerated by participants. This research is important for developing new ways to protect people from CMV and improve public health outcomes.

The research process

The trial runs in 3 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Vaccination schedule

    You will receive a total of three injections of either the mRNA-1647 vaccine or a placebo (a solution containing only sodium chloride, which is a salt solution).

    The mRNA-1647 vaccine is administered via intramuscular injection, meaning it is injected into the muscle, and each dose contains 100 micrograms of the active substance.

    The placebo is also administered via intramuscular injection but contains 0 micrograms of the active vaccine substance.

  2. Step 2

    Monitoring after injections

    For 7 days after each injection, you will monitor and report any expected side effects, such as redness or soreness at the injection site.

    For 28 days after each injection, any unexpected side effects that occur must be reported.

    Starting 28 days after the third injection, blood tests will be conducted to check for primary cytomegalovirus (cmv) infection. this is measured by checking if your blood changes from negative to positive for specific antibodies (proteins that help the body fight infection) that were not included in the vaccine.

  3. Step 3

    Long-term follow-up

    From the first day until 6 months after the last injection, any serious adverse events (major health problems) must be tracked.

    From the first day until the end of the study, any important adverse events of special interest (specific medical concerns) must be monitored.

    Blood tests to measure antibody levels (the body's immune response) will be performed at specific intervals: on day 1, at month 3, month 7, month 12, month 18, month 24, and month 30.

    If a cmv infection is detected, further testing using pcr (a method used to detect the presence of viral genetic material) will be performed on urine and blood samples to check how the virus is behaving in the body.

Who can join the trial?

11 criteria

  • You must be a female between 16 and 40 years old at the time you agree to join the study.
  • You must be able to follow all the rules and steps of the study as determined by the study doctor.
  • If you are 20 years of age or older, you must currently have or expect to have close contact with at least one child aged 5 years or younger within 7 months after your first dose. Close contact means being the parent or having contact such as feeding, changing diapers, or providing childcare for at least 8 hours every week.
  • You must have specific blood test results for Cytomegalovirus (CMV), which is a common virus:
    • If you are in the group without previous exposure, you must test negative for both CMV IgG (a marker showing past infection) and CMV IgM (a marker showing a new or recent infection).
    • If you are in the group with previous exposure, you must test positive for CMV IgG and either negative or positive for CMV IgM.
    • People who test positive only for CMV IgM (and negative for CMV IgG) cannot join immediately but can be tested again after 6 weeks.
    • You and your parent or legal guardian (if you are under the legal age) must provide written consent, which is a signed document stating you agree to participate.
    • The study doctor must confirm that you, or your parent/guardian, understand the study and are physically able to attend all follow-up appointments and procedures for the 30-month duration of the study.
    • For females who are able to become pregnant, a urine pregnancy test must be negative at the start of the study and on the day of your first injection.
    • If you are a female of childbearing age and are sexually active with men, you must have used effective contraception (birth control) or avoided pregnancy-related activities for at least 28 days before the first injection.
    • You must agree to continue using effective contraception for 3 months after your third injection.

Who cannot join the trial?

15 criteria

  • You are a female who is unable to have children, which means you have had surgery to prevent pregnancy, such as having your fallopian tubes tied, your ovaries removed, or your uterus removed, or you have gone through menopause (the time when a woman no longer has monthly periods).
  • You have a medical condition that is clinically unstable, meaning it is not well-controlled or is currently changing in a way that requires new medications or treatments.
  • You have a history of immunodeficiency, which means your body's immune system (the body's natural defense against germs) does not work correctly, or you have a condition that suppresses your immune system.
  • You have skin conditions, such as psoriasis (a condition that causes red, itchy, or scaly skin patches), specifically on your upper arms where the injection will be given.
  • You have a history of anaphylaxis or severe hypersensitivity, which are extremely serious and life-threatening allergic reactions, especially after receiving an mRNA vaccine.
  • You have a bleeding disorder that makes it unsafe for you to receive an injection into the muscle or to have blood drawn for tests.
  • You have any medical, mental health, or work-related condition that, in the doctor's opinion, could increase your risk or make it hard to understand the study results.
  • You have received any other vaccine within 28 days before or after the study injections, specifically following rules for COVID-19 vaccines (must be at least 28 days apart) and influenza (flu) vaccines (must be at least 14 days apart).
  • You have taken systemic immunosuppressants, which are medications that lower your body's ability to fight infection, for more than 14 days in the last 6 months, or you plan to take them during the study.
  • You have taken antiviral medications used to treat CMV (a type of virus) within 2 weeks of the first injection or plan to take them during the study.
  • You have previously taken part in a study testing a different CMV vaccine.
  • You have received systemic immunoglobulins or blood products within the last 3 months.
  • You have donated 450 mL or more of blood within 28 days before joining the study.
  • You have participated in another interventional clinical study (a medical study where you receive a specific treatment) within 28 days before the first injection or plan to do so during this study.
  • You are a member of the study team or live in the same house as someone who works on the study.
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Investigated drugs

mRNA-1647 is an experimental vaccine that uses messenger RNA (mRNA) technology to help the body learn how to protect itself against the cytomegalovirus (CMV) infection. It works by providing instructions to the body's cells to produce specific proteins found on the surface of the virus, which triggers the immune system to recognize and fight the actual virus if the person is exposed to it in the future.

What is already known about the treatment

  • mRNA-1647

    This experimental vaccine is given as an injection into the muscle to help prevent infections caused by the cytomegalovirus. Currently being studied in clinical trials, it works by using messenger RNA to teach the body's cells how to create specific proteins found on the surface of the virus. Once these proteins are made, the immune system learns to recognize and fight the actual virus if it ever enters the body. It is classified as an mRNA vaccine.

  • Sodium Chloride 0.9%

    This substance is a simple salt solution administered through an injection into the muscle to serve as a placebo in this study. It is a widely used, well-established medical solution that contains no active medicinal ingredients for fighting viruses. In a clinical trial, it is used as a comparison tool to help researchers determine if the actual vaccine is truly effective. It is pharmacologically classified as a saline solution.

Investigated diseases

Cytomegalovirus Infection - This is an infection caused by a common type of virus from the herpes family. Once the virus enters the body, it can remain active and spread through bodily fluids. The infection can progress from an initial stage where the immune system begins to recognize the virus to a stage where the virus spreads through the bloodstream or appears in urine. In some cases, the virus can move from the blood into different organs or systems. The presence of the virus is often marked by the body producing specific antibodies in response to the infection.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2023-508820-37-00Protocol codemRNA1647-P301Estimated enrolment7 484 patientsSponsorModerna Inc.

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