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Respiratory Syncytial VirusPhase 1NCT05743881

A Safety, Tolerability, and Immunogenicity Study of mRNA-1345 and mRNA-1365 in Participants Aged 5 Months to <24 Months

A Phase 1 study testing mRNA-1345, mRNA-1365 and Nimenrix in people with Respiratory Syncytial Virus and Human Metapneumovirus, run by ModernaTX, Inc. at 17 sites in 3 countries.

Active, not recruiting

Under way, not looking for participants. Everyone needed has enrolled. The study is still running.

Official record
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Trial summary

The purpose of this study is to assess the safety and immunogenicity of mRNA-1365, an mRNA vaccine targeting respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) and mRNA-1345, an mRNA vaccine targeting RSV, in participants aged 5 months to <24 months. Read more about this study

Who is it for?
Ages 5 to 24 months
What is being tested?
mRNA-1345, mRNA-1365 and Nimenrix
Could I receive a placebo?
Yes, some participants may receive a placebo
How many people
186 participants
Where
17 sitesin 3 countries
Study dates
15 Feb 2023to 31 Aug 2029
Phase
Phase 1
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 5 to 24 months
  • All sexes
  • No healthy volunteers
  • Child

Who may be able to join

  • The participant is 8 months to <24 months (Part A), 5 months to <8 months (Part B), or 8 months to <12 months (Part C) of age at the time of randomization (Day 1/Baseline visit), who is in good general health, in the opinion of the Investigator, based on review of medical history and screening physical examination.
  • In the Investigator's opinion, the parent(s)/ legally authorized representative (LAR)(s) understand and are willing and physically able to comply with protocol-mandated follow up, including all procedures, and provide written informed consent.
  • The participant is growing normally for age in the opinion of the site clinician in the months prior to enrollment.
  • The participant was born at full-term (≥37 weeks gestation) with a minimum birth weight of 2.5 kilograms (kg).
  • For Part C Cohort 7: participant must have received nirsevimab ≥6 months prior to Day 1 Visit.
  • For Part C Cohort 8: participant was eligible at any time since birth, according to national guidelines, to receive nirsevimab prior to Day 1 Visit but did not do so.
  • For Part B Extension: participants enrolled and dosed in Part B (Cohorts 3 to 6); either reached the end of study of the Main Study or were dosed and subsequently discontinued from the Main Study. This includes participants who were lost to follow-up, if they can be re-engaged.
  • For Part B Extension: participant's parent(s)/LAR(s) has provided written informed consent for participation in Part B of the Main Study and the Part B Extension.

Who cannot join

  • Has a known history of symptomatic RSV (Part A: within 3 months; Part B and Part C: since birth) or hMPV infection (Part A: within 3 months; Part B: since birth) prior to administration of the first dose of investigational product (IP) or has a known close contact with anyone with laboratory-confirmed RSV (Parts A, B, and C) or hMPV infection (Parts A or B) within 14 days prior to administration of the first dose of IP.
  • Is acutely ill or febrile 24 hours prior to or at the screening visit. Fever is defined as a body temperature ≥38.0°Celsius/≥100.4°Fahrenheit. Participants who meet this criterion may have visits rescheduled within the relevant study visit windows.
  • Has previously been administered an investigational or approved vaccine for prevention of RSV (Parts A, B, and C) or hMPV (Parts A and B) infection or if the participant's mother received an investigational or approved vaccine for the prevention of RSV (Parts A, B, and C) or hMPV (Parts A and B) infection during pregnancy.
  • Has received investigational or approved agents for prophylaxis against RSV or hMPV (for example, monoclonal antibodies) or is intending to receive these during the course of the study. For Part C (Cohort 7 only), use of nirsevimab ≥6 months before Day 1 Visit is allowed.
  • Has a known hypersensitivity to a component of the vaccine or its excipients. Hypersensitivity includes, but is not limited to, anaphylaxis or immediate allergic reaction of any severity to a previous dose of an mRNA vaccine or any of its components (including polyethylene glycol or immediate allergic reaction of any severity to polysorbate).
  • Has a medical condition that, according to the Investigator's judgment, may pose additional risk as a result of participation, interfere with safety assessments, or interfere with interpretation of results.
  • Note: Other protocol-defined inclusion/exclusion criteria apply.
  • For Part B Extension, there are no specific exclusion criteria.

Trial locations and contacts

17 sites in 3 countries.

17 sites in 3 countries

United States12 sites

  • Duke Vaccine and Trials Unit

    Durham, North Carolina, 27703

  • CyFair

    Houston, Texas, 77065

  • Pediatric Associates

    Houston, Texas, 77087

  • MedPharmics - Platinum - PPDS

    Lafayette, Louisiana, 70508

  • Matrix Clinical Research

    Los Angeles, California, 90057

  • DM Clinical Research- River Forest

    Melrose Park, Illinois, 60160

  • Vanderbilt Vaccine Research Program

    Nashville, Tennessee, 37232

  • Palmetto Pediatrics, PA

    North Charleston, South Carolina, 29406-9170

  • Village Pediatrics

    Plano, Texas, 75024

  • Velocity Clinical Research - Providence

    Providence, Rhode Island, 02886

  • Pediatric Center

    Richmond, Texas, 77469

  • Meridian Clinical Research

    Washington D.C., District of Columbia, 20016

Other trials in United States

Panama4 sites

  • CEVAXIN David

    David, Chiriquí Province, 0401

  • CEVAXIN Chorrera

    La Chorrera, Panamá Oeste Province

  • CEVAXIN Avenida Mexico

    Panama City, 0801

  • CEVAXIN 24 de Diciembre

    Panama City

Other trials in Panama

United Kingdom1 site

  • Norfolk and Norwich University Hospitals

    Norwich, NR4 7UY

Other trials in United Kingdom

About this study

Official title: A Phase 1, Randomized, Observer-blind, Placebo-controlled, Age De-escalation Study of the Safety, Tolerability, and Immunogenicity of mRNA-1345 and mRNA-1365 in Participants Aged 5 Months to <24 Months

The purpose of this study is to assess the safety and immunogenicity of mRNA-1365, an mRNA vaccine targeting respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) and mRNA-1345, an mRNA vaccine targeting RSV, in participants aged 5 months to <24 months.

Being tested
mRNA-1345, mRNA-1365, Placebo, Nimenrix
Keywords
mRNA-1345, mRNA-1365, RSV vaccine, hMPV vaccine, RSV/hMPV vaccine

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • mRNA-1345Biological

    Sterile liquid for injection

  • mRNA-1365Biological

    Sterile liquid for injection

  • PlaceboBiological

    0.9% sodium chloride (normal saline) solution for injection

  • NimenrixDrug

    Solution for injection

Study groups in NCT05743881
Study groupRoleWhat they receive
Part A: mRNA-1345, Dose 1 (Age Group: 8 to <24 months)ExperimentalParticipants will receive mRNA-1345 vaccine by intramuscular (IM) injection on Days 1, 57 and 113.
Receives: Biological: mRNA-1345
Part A: mRNA-1365, Dose 1 (Age Group: 8 to <24 months)ExperimentalParticipants will receive mRNA-1365 vaccine by IM injection on Days 1, 57 and 113.
Receives: Biological: mRNA-1365
Part A: Placebo (Age Group: 8 to <24 months)Placebo comparatorParticipants will receive mRNA-1345/ mRNA-1365 vaccine matching placebo by IM injection on Days 1, 57 and 113. In countries where applicable, participants may receive Nimenrix instead of placebo on Day 113.
Receives: Biological: Placebo; Drug: Nimenrix
Part B: mRNA-1345, Dose 2 (Age Group: 5 to <8 months)ExperimentalParticipants will receive mRNA-1345 by IM injection on Days 1, 57 and 113.
Receives: Biological: mRNA-1345
Part B: mRNA-1365, Dose 2 (Age Group: 5 to <8 months)ExperimentalParticipants will receive mRNA-1365 by IM injection on Days 1, 57 and 113.
Receives: Biological: mRNA-1365
Part B: mRNA-1345 Dose 1 (Age Group: 5 to <8 months)ExperimentalParticipants will receive mRNA-1345 by IM injection on Days 1, 57 and 113.
Receives: Biological: mRNA-1345
Part B: mRNA-1365 Dose 1 (Age Group: 5 to <8 months)ExperimentalParticipants will receive mRNA-1365 by IM injection on Days 1, 57 and 113.
Receives: Biological: mRNA-1365
Part B: Placebo (Age Group: 5 to <8 months)Placebo comparatorParticipants will receive mRNA-1345/ mRNA-1365 vaccine matching placebo by IM injection on Days 1, 57 and 113. In countries where applicable, participants may receive Nimenrix instead of placebo on Day 113.
Receives: Biological: Placebo; Drug: Nimenrix
Part B Extension: mRNA-1345, Dose 2 (Age Group: 5 to <8 months)No interventionParticipants will have the option to re-enrol in the Part B extension period.
Part B Extension: mRNA-1365, Dose 2 (Age Group: 5 to <8 months)No interventionParticipants will have the option to re-enrol in the Part B extension period.
Part B Extension: mRNA-1345 Dose 1 (Age Group: 5 to <8 months)No interventionParticipants will have the option to re-enrol in the Part B extension period.
Part B Extension: mRNA-1365 Dose 1 (Age Group: 5 to <8 months)No interventionParticipants will have the option to re-enrol in the Part B extension period.
Part B Extension : Placebo (Age Group: 5 to <8 months)No interventionParticipants will have the option to re-enrol in the Part B extension period.
Part C: mRNA-1345 Dose 1 (Age Group 8 to <12 months exposed to nirsevimab)ExperimentalParticipants who have been previously exposed to nirsevimab will receive mRNA 1345 by IM injection on Days 1, 57, and 113.
Receives: Biological: mRNA-1345
Part C: mRNA-1345 Dose 1 (Age Group 8 to <12 months not exposed to nirsevimab)ExperimentalParticipants who have not been previously exposed to nirsevimab will receive mRNA 1345 by IM injection on Days 1, 57, and 113.
Receives: Biological: mRNA-1345

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Main Study: Number of Participants with Solicited Local and Systemic Adverse Reactions (ARs)

    Measured: Up to Day 120 (7 days after each injection)

  2. Main Study: Number of Participants with Unsolicited Adverse Events (AEs)

    Measured: Up to Day 141 (28 days after each injection)

  3. Main Study: Number of Participants with Medically-Attended Adverse Events (MAAEs)

    Measured: Day 1 through Day 730

  4. Main Study: Number of Participants with Adverse Event of Special Interests (AESIs), Serious Adverse Events (SAEs) and Adverse Events Leading to Discontinuation

    Measured: Day 1 through Day 730

  5. Part B Extension: Number of Participants with MAAEs, AESIs and SAEs

    Measured: Day 1 of the Extension to end of study (EoS) (up to 3 years)

  6. Part B Extension: Number of Participants with Lower Respiratory Tract Illness (LRTI), Severe LRTI, Very Severe LRTI, and Hospitalizations Associated with RSV or hMPV

    Measured: Day 1 of the Extension to EoS (up to 3 years)

Secondary outcomes (11)

  1. Main Study: Number of Participants with Respiratory tract Illness (RTI), LRTI, Severe LRTI, Very Severe LRTI, and Hospitalizations Associated with RSV or hMPV

    Measured: Day 1 through Day 730

  2. Main Study (Parts A and B): Geometric Mean Titer (GMT) of Serum RSV and hMPV Neutralizing Antibodies

    Measured: Baseline up to Month 12

  3. Main Study (Part C): GMT of Serum RSV Neutralizing Antibodies

    Measured: Baseline up to Month 12

  4. Main Study (Parts A and B): Geometric Mean Concentration (GMC) of Serum RSV F- and hMPV F-Binding Antibodies

    Measured: Baseline up to Month 12

  5. Main Study (Part C): GMC of Serum RSV F-Binding Antibodies

    Measured: Baseline up to Month 12

  6. Main Study: Geometric Mean Fold-Rise (GMFR) of Postbaseline/baseline Neutralizing Antibody Titers and Binding Antibody

    Measured: Month 12

  7. Main Study: Number of Participants with Vaccine-specific T-cell Responses Measured by Flow Cytometry

    Measured: Baseline up to Month 12

  8. Part B Extension: Geometric Mean Titer (GMT) of Serum RSV and hMPV Neutralizing Antibodies

    Measured: Day 1 of the Extension up to EoS (up to 3 years)

  9. Part B Extension: Geometric Mean Concentration (GMC) of Serum RSV F- and hMPV F-Binding Antibodies

    Measured: Day 1 of the Extension up to EoS (up to 3 years)

  10. Part B Extension: Geometric Mean Fold-Rise (GMFR) of Postbaseline/baseline Neutralizing Antibody Titers and Binding Antibody

    Measured: Day 1 of the Extension up to EoS (up to 3 years)

  11. Part B Extension: Number of Participants with Vaccine-specific T-cell Responses Measured by Flow Cytometry

    Measured: Day 1 of the Extension up to EoS (up to 3 years)

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted24 Feb 2023
  2. Study start15 Feb 2023
  3. Primary completion31 Aug 2029 (estimated)
  4. Study completion31 Aug 2029 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 1
Primary purpose
Treatment
Allocation
Randomised
Intervention model
Parallel groups
Masking
Triple blind
Who is masked
Participant, Investigator, Outcomes assessor
Enrolment
186 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT05743881
Sponsor's protocol ID
mRNA-1365-P101
Other IDs
2022-502022-41, 2022-502022-41-00
Status last verified
Jun 2026
First submitted
15 Feb 2023
Last updated
26 Jun 2026
Results posted
No
FDA-regulated drug
Yes
FDA-regulated device
No

Publications

  • Amodio D, Angelidou A, Cotugno N, Sherman AC, Levy O, Palma P; IPVC 2023 Speakers' group. Biomarkers of vaccine safety and efficacy in vulnerable populations: Lessons from the fourth international precision vaccines conference. Vaccine. 2025 Jan 1;43(Pt 2):126477. doi: 10.1016/j.vaccine.2024.126477. Epub 2024 Nov 28.

    PubMed 39608233

Questions about this trial

What is this clinical trial studying?

A Phase 1 study testing mRNA-1345, mRNA-1365 and Nimenrix in people with Respiratory Syncytial Virus and Human Metapneumovirus, run by ModernaTX, Inc. at 17 sites in 3 countries.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 8 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: under way, not looking for participants, as of the sponsor's last update on 26 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 17 sites in United States, Panama, United Kingdom. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Main Study: Number of Participants with Solicited Local and Systemic Adverse Reactions (ARs) (time frame: Up to Day 120 (7 days after each injection)). The study lists 6 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT05743881, which also lists 1 linked publication.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 26 Jun 2026.

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