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Study on the Safety and Immune Response of mRNA-1345 and mRNA-1365 for Infants with Acute Lower Respiratory Infection Aged 5 to 24 Months

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 safety and effectiveness of two investigational vaccines, mRNA-1345 and mRNA-1365, in young children aged 5 months to less than 24 months. These vaccines are being tested to see how well they work in preventing infections caused by respiratory viruses, specifically those that can lead to acute lower respiratory infection, which is a condition affecting the lungs and airways.

The study involves giving participants injections of the vaccines and monitoring them for any reactions or side effects. Some participants will receive the actual vaccines, while others will receive a placebo, which is a substance with no active ingredients. The purpose of the study is to evaluate the safety and how the body responds to these vaccines, which are designed to help the immune system fight off infections.

Throughout the study, participants will be closely observed for any signs of illness or adverse reactions. The study aims to gather information on how the vaccines affect the immune system and whether they can help prevent serious respiratory infections in young children. This research is important for developing new ways to protect children from these infections and improve their overall health.

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

    Initial visit

    Upon joining the study, the participant will attend an initial visit. During this visit, the participant's health will be assessed to ensure they meet the study requirements. This includes a review of medical history and a physical examination.

    The participant's parent or legal representative will be required to provide written informed consent, confirming their understanding and agreement to follow the study procedures.

  2. Step 2

    First injection

    The participant will receive the first injection. This injection may contain either the study vaccine mRNA-1345, mRNA-1365, or a placebo, which is a harmless solution used for comparison.

    The injection is administered as an intramuscular injection, meaning it is given directly into a muscle.

  3. Step 3

    Monitoring period

    After the injection, the participant will be monitored for any immediate reactions. This monitoring period helps ensure the participant's safety and allows for the observation of any side effects.

    The participant's parent or legal representative will be asked to report any changes in the participant's health or any side effects they notice.

  4. Step 4

    Follow-up visits

    The participant will attend several follow-up visits over the course of the study. These visits are scheduled to monitor the participant's health and to collect information on how the participant's body is responding to the injection.

    During these visits, additional health assessments may be conducted, and the participant's parent or legal representative will be asked to provide updates on the participant's health.

  5. Step 5

    Second injection

    The participant will receive a second injection, similar to the first one. This injection is also administered as an intramuscular injection.

    The second injection may occur at a specified time after the first injection, as determined by the study protocol.

  6. Step 6

    Final assessment

    At the end of the study, a final assessment will be conducted. This assessment will evaluate the participant's overall health and any effects of the injections received during the study.

    The participant's parent or legal representative will be asked to provide any final observations or concerns regarding the participant's health.

Who can join the trial?

12 criteria

  • The participant must be a male or female child.
  • The participant's age must be:
    • 8 months to less than 24 months for Part A
    • 5 months to less than 8 months for Part B
    • 8 months to less than 12 months for Part C
    • 5 months to less than 24 months for Part D
    • The participant must be in good general health as determined by the study doctor, based on medical history and a physical exam. Common mild conditions like mild to moderate GERD (a condition where stomach acid flows back into the tube connecting your mouth and stomach) or atopic dermatitis (a skin condition causing itchy, inflamed skin) are allowed if they do not interfere with the study.
    • The participant's parent(s) or legally authorized representative(s) must understand and be willing and able to follow the study requirements, including all procedures, and must provide written consent.
    • The participant must be growing normally for their age, according to the study doctor, in the months before joining the study.
    • The participant must have been born at full-term (37 weeks or more of pregnancy) with a minimum birth weight of 2.5 kg (about 5.5 pounds).
    • The participant's parent(s) or legally authorized representative(s) must have a consistent way to be contacted, either by phone or email/computer.
    • For Part C Cohort 7 and Part D Cohorts 11 and 12: The participant must have received nirsevimab (a medication) at least 6 months before the first study visit.
    • For Part C Cohort 8: The participant was eligible to receive nirsevimab at any time since birth, according to national guidelines, but did not receive it before the first study visit.

Who cannot join the trial?

1 criterion

  • Patients with an **acute lower respiratory infection** cannot participate. This means if you have a sudden infection in your lungs or airways, you are not eligible.
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Investigated drugs

  • mRNA-1345

    is a new type of vaccine that uses a small piece of genetic material called messenger RNA (mRNA) to help the body recognize and fight off certain viruses. This vaccine is designed to teach the immune system to identify and respond to specific virus proteins, which can help protect against infections. In this trial, researchers are studying how safe and well-tolerated this vaccine is in young children, as well as how well it helps their immune systems respond to the virus.

  • mRNA-1365

    is another vaccine that also uses messenger RNA technology. Like mRNA-1345, it aims to train the immune system to recognize and combat specific virus proteins. The goal of this vaccine is to provide protection against infections by helping the body prepare a defense before encountering the actual virus. The trial is focused on understanding the safety and immune response of this vaccine in young children.

What is already known about the treatment

  • mRNA-1345

    This medication is administered as an injection and is currently being studied in clinical trials to assess its safety and how well it is tolerated in young children. It is being investigated for its potential to prevent acute lower respiratory infections. The medication works by using a small piece of genetic material called mRNA to instruct cells in the body to produce a protein that triggers an immune response, helping the body to fight off infections. It falls under the category of mRNA vaccines, which are a new type of vaccine designed to protect against infectious diseases.

  • mRNA-1365

    This medication is also given as an injection and is part of ongoing research to determine its safety and effectiveness in children under two years old. It is intended to help prevent acute lower respiratory infections by using mRNA technology. The mechanism involves delivering mRNA into the body, which then guides cells to make a protein that stimulates the immune system to recognize and combat the infection. Like mRNA-1345, it is classified as an mRNA vaccine, representing a modern approach to vaccination.

Investigated diseases

Acute lower respiratory infection – This disease affects the lower part of the respiratory system, including the airways and lungs. It is characterized by symptoms such as coughing, difficulty breathing, and chest discomfort. The infection can be caused by various pathogens, including viruses and bacteria. As the disease progresses, inflammation in the airways and lungs can lead to increased mucus production and impaired oxygen exchange. In severe cases, it may result in significant breathing difficulties and require medical intervention. The condition can vary in severity and duration, depending on the underlying cause and the individual's health status.
Trial detailsLast updated 2 Oct 2026
Age0-17PhasePhase ITrial ID2022-502022-41-00Protocol codemRNA-1365-P101Estimated enrolment690 patientsSponsorModerna Inc.

sourced from the EU Clinical Trials Register and site verification

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On this site, “treatment” means an investigational medicine being studied in a clinical trial. Its safety and efficacy for the use being studied have not yet been confirmed, some participants may receive a placebo or a comparator medicine, and taking part does not guarantee any health benefit. The decision to take part is made by the doctor at the research site. This site is for information only and does not replace medical advice.

This service is not affiliated with the European Commission, the EMA, or the official CTIS system. Most information comes from publicly available international clinical-trial registries, supplemented by data from academic sites, national regulators and commercial sponsors. On this site, “treatment” and “therapy” mean a medicine being tested in a clinical trial. Its safety and effectiveness in the use being studied are not yet confirmed, some participants may receive a placebo or a comparator, and taking part does not guarantee a health benefit. The doctor at the research site decides who can take part. This site provides information, not medical advice. Certain content and visual elements on this website have been generated or enhanced using artificial intelligence (AI).