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

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.

Study Overview

• Status: Active, not recruiting
• Conditions: Respiratory Syncytial Virus; Human Metapneumovirus
• Intervention / Treatment: Biological: mRNA-1345; Biological: mRNA-1365; Biological: Placebo; Drug: Nimenrix

• Study Type: Interventional
• Enrollment (Actual): 186
• Phase: Phase 1

Contacts and Locations

Study Locations

• Australia
  • Western Australia
    • Nedlands, Western Australia, Australia, 6009
      • Telethon Kids Institute
• Canada
  • British Columbia
    • Vancouver, British Columbia, Canada, V5Z 4H4
      • BC Children's Hospital - Vaccine Evaluation Centre - Neonatology
  • Nova Scotia
    • Halifax, Nova Scotia, Canada, B3K 6R8
      • Dalhousie University IWK Health Centre
  • Ontario
    • London, Ontario, Canada, N6A 5W9
      • London Health Sciences Centre - Victoria Hospital
  • Quebec
    • Montreal, Quebec, Canada
      • Universite de Montreal - Centre Hospitalier Universitaire (CHU) Sainte-Justine
• Panama
  • Panama City, Panama, 0801
    • CEVAXIN Avenida Mexico
  • Panama City, Panama
    • CEVAXIN 24 de diciembre
  • Chiriquí Province
    • David, Chiriquí Province, Panama, 0401
      • CEVAXIN David
  • Panamá Oeste Province
    • La Chorrera, Panamá Oeste Province, Panama
      • CEVAXIN Chorrera
• South Africa
  • Gauteng
    • Hillbrow, Gauteng, South Africa, 2001
      • Shandukani Research CRS
    • Johannesburg, Gauteng, South Africa, 2013
      • Wits Health Consortium
    • Soshanguve, Gauteng, South Africa, 0152
      • Setshaba Research Centre
  • Western Cape
    • Cape Town, Western Cape, South Africa, 7440
      • Family Centre for Research with Ubuntu (FAMCRU)- Tygerberg
    • Cape Town, Western Cape, South Africa, 7530
      • Practice Dr Jan Vermeulen
• United Kingdom
  • Liverpool, United Kingdom, L12 2AP
    • Alder Hey NHS Foundation Trust - Pharmacy Clinical Trials
  • London, United Kingdom, SW170RE
    • St George's Hospital
  • London, United Kingdom
    • Imperial College London and Imperial College Healthcare NHS
  • Norwich, United Kingdom, NR4 7UY
    • Norfolk and Norwich University Hospitals
  • Oxford, United Kingdom, OX3 9DU
    • John Radcliffe Hospital
  • Southampton, United Kingdom, SO16 6YD
    • Southampton General Hospital
• United States
  • California
    • Los Angeles, California, United States, 90057
      • Matrix Clinical Research
    • Los Angeles, California, United States, 90095
      • Los Angeles Children's Hospital
  • Colorado
    • Englewood, Colorado, United States, 80110
      • Velocity Clinical Research, Denver
  • District of Columbia
    • Washington D.C., District of Columbia, United States, 20016-4358
      • Meridian Clinical Research
    • Washington D.C., District of Columbia, United States, 20016
      • Meridian Clinical Research
  • Florida
    • Jacksonville, Florida, United States, 32209
      • University of Florida Health Science Center
    • Orlando, Florida, United States, 32829-8070
      • Accel Research Sites - Nona Pediatric Center
  • Idaho
    • Idaho Falls, Idaho, United States, 83404
      • Clinical Research Prime
  • Louisiana
    • Lafayette, Louisiana, United States, 70508
      • MedPharmics - Platinum - PPDS
  • Massachusetts
    • Worcester, Massachusetts, United States, 01655
      • UMass Chan Medical School
    • Worcester, Massachusetts, United States, 01655-0002
      • UMass Memorial Medical Center
  • Michigan
    • Detroit, Michigan, United States, 48202-2608
      • Henry Ford Health System
    • Southfield, Michigan, United States, 48075-5400
      • Great Lakes Research Institute
  • Minnesota
    • Minneapolis, Minnesota, United States, 55454-1404
      • Pediatric Specialty Care Discovery Clinic
  • Missouri
    • St Louis, Missouri, United States, 63110
      • Washington University School of Medicine in St. Louis
  • Nebraska
    • Hastings, Nebraska, United States, 68901-2640
      • Meridian Clinical Research
  • North Carolina
    • Durham, North Carolina, United States, 27703
      • Duke Vaccine and Trials Unit
  • Ohio
    • South Euclid, Ohio, United States, 44121
      • Senders Pediatrics
  • Rhode Island
    • Providence, Rhode Island, United States, 02886
      • Velocity Clinical Research - Providence
  • South Carolina
    • North Charleston, South Carolina, United States, 29406-9170
      • Palmetto Pediatrics, PA
  • Tennessee
    • Nashville, Tennessee, United States, 37232
      • Vanderbilt Vaccine Research Program
  • Texas
    • El Paso, Texas, United States, 79905
      • Texas Tech University Health Sciences Center
    • Houston, Texas, United States, 77087
      • Pediatric Associates
    • Houston, Texas, United States, 77054
      • Mercury Clinical Research, Inc.
    • Houston, Texas, United States, 77065
      • CyFair
    • Plano, Texas, United States, 75024
      • Village Pediatrics
    • Richmond, Texas, United States, 77469
      • Pediatric Center
    • Richmond, Texas, United States, 77469-3348
      • Mercury Clinical Research, Inc.
    • Tomball, Texas, United States, 77375
      • North Houston Internal Medicine & Pediatric Clinic
  • Washington
    • Seattle, Washington, United States, 98105
      • Childrens Hospital Regional Medical Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 5 months to 2 years (Child)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• 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.

Exclusion Criteria:

• 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.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

10

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Part A: mRNA-1345, Dose 1 (Age Group: 8 to <24 months); Participants will receive mRNA-1345 vaccine by intramuscular (IM) injection on Days 1, 57 and 113.	Biological: mRNA-1345; Sterile liquid for injection
Experimental: Part A: mRNA-1365, Dose 1 (Age Group: 8 to <24 months); Participants will receive mRNA-1365 vaccine by IM injection on Days 1, 57 and 113.	Biological: mRNA-1365; Sterile liquid for injection
Placebo Comparator: Part A: Placebo (Age Group: 8 to <24 months); Participants 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.	Biological: Placebo; 0.9% sodium chloride (normal saline) solution for injection; Drug: Nimenrix; Solution for injection
Experimental: Part B: mRNA-1345, Dose 2 (Age Group: 5 to <8 months); Participants will receive mRNA-1345 by IM injection on Days 1, 57 and 113.	Biological: mRNA-1345; Sterile liquid for injection
Experimental: Part B: mRNA-1365, Dose 2 (Age Group: 5 to <8 months); Participants will receive mRNA-1365 by IM injection on Days 1, 57 and 113.	Biological: mRNA-1365; Sterile liquid for injection
Experimental: Part B: mRNA-1345 Dose 1 (Age Group: 5 to <8 months); Participants will receive mRNA-1345 by IM injection on Days 1, 57 and 113.	Biological: mRNA-1345; Sterile liquid for injection
Experimental: Part B: mRNA-1365 Dose 1 (Age Group: 5 to <8 months); Participants will receive mRNA-1365 by IM injection on Days 1, 57 and 113.	Biological: mRNA-1365; Sterile liquid for injection
Placebo Comparator: Part B: Placebo (Age Group: 5 to <8 months); Participants 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.	Biological: Placebo; 0.9% sodium chloride (normal saline) solution for injection; Drug: Nimenrix; Solution for injection
Experimental: Part C: mRNA-1345 Dose 1 (Age Group 8 to <12 months exposed to nirsevimab); Participants who have been previously exposed to nirsevimab will receive mRNA 1345 by IM on Days 1, 57, and 113.	Biological: mRNA-1345; Sterile liquid for injection
Experimental: Part C: mRNA-1345 Dose 1 (Age Group 8 to <12 months not exposed to nirsevimab); Participants who have not been previously exposed to nirsevimab will receive mRNA 1345 by IM on Days 1, 57, and 113.	Biological: mRNA-1345; Sterile liquid for injection

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Number of Participants with Solicited Local and Systemic Adverse Reactions (ARs)	Up to Day 120 (7 days after each injection)
Number of Participants with Unsolicited Adverse Events (AEs)	Up to Day 141 (28 days after each injection)
Number of Participants with Medically-Attended Adverse Events (MAAEs)	Day 1 through Day 730
Number of Participants with Adverse Event of Special Interests (AESIs), Serious Adverse Events (SAEs) and Adverse Events Leading to Discontinuation	Day 1 through Day 730

Secondary Outcome Measures

Outcome Measure	Time Frame
Geometric Mean Fold-Rise (GMFR) Postbaseline/baseline Neutralizing Antibody Titers	Baseline up to Month 12
Number of Participants with Respiratory Tract Illness (RTI), Lower Respiratory Tract Illness (LRTI), Severe LRTI, Very Severe LRTI, and Hospitalizations Associated with RSV or hMPV	Day 1 through Day 730
Parts A and B: Geometric Mean Titer (GMT) of Serum RSV and hMPV Neutralizing Antibodies	Baseline up to Month 12
Part C: GMT of Serum RSV Neutralizing Antibodies	Baseline up to Month 12
Parts A and B: Geometric Mean Concentration (GMC) of Serum RSV F- and hMPV F-Binding Antibodies	Baseline up to Month 12
Part C: GMC of Serum RSV F-Binding Antibodies	Baseline up to Month 12
Number of Participants with Vaccine-specific T-cell Responses Measured by Flow Cytometry	Baseline up to month 12

Collaborators and Investigators

• Sponsor: ModernaTX, Inc.

Publications and helpful links

General 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.

Study record dates

Study Major Dates

• Study Start (Actual): February 15, 2023
• Primary Completion (Estimated): August 31, 2026
• Study Completion (Estimated): September 30, 2026

Study Registration Dates

• First Submitted: February 15, 2023
• First Submitted That Met QC Criteria: February 15, 2023
• First Posted (Actual): February 24, 2023

Study Record Updates

• Last Update Posted (Actual): November 24, 2025
• Last Update Submitted That Met QC Criteria: November 21, 2025
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: mRNA-1345; mRNA-1365; RSV vaccine; hMPV vaccine; RSV/hMPV vaccine
• Additional Relevant MeSH Terms: mRNA-1345 respiratory syncytial virus vaccine
• Other Study ID Numbers: mRNA-1365-P101; 2022-502022-41 (EudraCT Number); 2022-502022-41-00 (Other Identifier: EU CT Number)

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No