> Trialight public data. Index of pages: https://trialight.com/llms.txt > Web page: https://trialight.com/data/trial/a-safety-tolerability-and-immunogenicity-study-of-mrna-1345-052dcf45-abe4-428a-9ed4-3afd71c12084 > Record changed: 2026-10-13 # A Safety, Tolerability, and Immunogenicity Study of mRNA-1345 and mRNA-1365 in Participants Aged 5 Months to <24 Months NCT05743881 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) Phase Phase 1 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) Recruitment status Active, not recruiting Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) Participants 186 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) Lead sponsor ModernaTX, Inc. Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) Start date 2023-02-15 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) Number of sites 17 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) ## Title and summary **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. Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Short title** A Safety, Tolerability, and Immunogenicity Study of mRNA-1345 and mRNA-1365 in Participants Aged 5 Months to <24 Months Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **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 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) ## Status and phase **Control arm** Placebo Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Registry reports results** No Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Listing at source** Listed Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Recruitment status** Active, not recruiting Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Phase** Phase 1 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Study type** Interventional Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) ## Dates **Completion date** 2029-08-31 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **First posted** 2023-02-24 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Registry last updated** 2026-06-26 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Primary completion date** 2029-08-31 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Start date** 2023-02-15 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) ## Size and sites **Actual participants** 186 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Participants** 186 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Participant count basis** Actual Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Protocol amendments** 5 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Number of sites** 17 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) ## Sponsor and oversight **Registry sponsor category** Industry Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Lead sponsor** ModernaTX, Inc. Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Source registry** ClinicalTrials.gov Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) ## Identifiers **Registry ID** NCT05743881 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **ClinicalTrials.gov ID** NCT05743881 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) **Registry record** Open registry record Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) ## Study design **Allocation** Randomised **Model** Parallel groups **Purpose** Treatment **Masking** Triple masking **Masking description** Parts A and B are blinded, and Part C is open-label. Part B Extension is unblinded. **Masked roles** Participants, Investigators, Outcome assessors Sources for study design Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) ## Outcomes ### Primary outcomes 1. Main Study: Number of Participants with Solicited Local and Systemic Adverse Reactions (ARs) Timeframe: Up to Day 120 (7 days after each injection) 2. Main Study: Number of Participants with Unsolicited Adverse Events (AEs) Timeframe: Up to Day 141 (28 days after each injection) 3. Main Study: Number of Participants with Medically-Attended Adverse Events (MAAEs) Timeframe: 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 Timeframe: Day 1 through Day 730 5. Part B Extension: Number of Participants with MAAEs, AESIs and SAEs Timeframe: 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 Timeframe: Day 1 of the Extension to EoS (up to 3 years) ### Secondary outcomes 1. Main Study: Number of Participants with Respiratory tract Illness (RTI), LRTI, Severe LRTI, Very Severe LRTI, and Hospitalizations Associated with RSV or hMPV Timeframe: Day 1 through Day 730 2. Main Study (Parts A and B): Geometric Mean Titer (GMT) of Serum RSV and hMPV Neutralizing Antibodies Timeframe: Baseline up to Month 12 3. Main Study (Part C): GMT of Serum RSV Neutralizing Antibodies Timeframe: 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 Timeframe: Baseline up to Month 12 5. Main Study (Part C): GMC of Serum RSV F-Binding Antibodies Timeframe: Baseline up to Month 12 6. Main Study: Geometric Mean Fold-Rise (GMFR) of Postbaseline/baseline Neutralizing Antibody Titers and Binding Antibody Timeframe: Month 12 7. Main Study: Number of Participants with Vaccine-specific T-cell Responses Measured by Flow Cytometry Timeframe: Baseline up to Month 12 8. Part B Extension: Geometric Mean Titer (GMT) of Serum RSV and hMPV Neutralizing Antibodies Timeframe: 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 Timeframe: 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 Timeframe: 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 Timeframe: Day 1 of the Extension up to EoS (up to 3 years) Sources for outcomes Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) ## Eligibility **Sex** All **Age groups** Children **Minimum age** 5 Months **Maximum age** 24 Months **Healthy volunteers** No ### 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. ### Inclusion criteria - 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. ### Exclusion criteria • For Part B Extension, there are no specific exclusion criteria. Sources for eligibility Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) ## Sites - Matrix Clinical ResearchLos Angeles, United States - Meridian Clinical ResearchWashington D.C., United States - DM Clinical Research- River ForestMelrose Park, United States - MedPharmics - Platinum - PPDSLafayette, United States - Duke Vaccine and Trials UnitDurham, United States - Velocity Clinical Research - ProvidenceProvidence, United States - Palmetto Pediatrics, PANorth Charleston, United States - Vanderbilt Vaccine Research ProgramNashville, United States - CyFairHouston, United States - Pediatric AssociatesHouston, United States - Village PediatricsPlano, United States - Pediatric CenterRichmond, United States - CEVAXIN DavidDavid, Panama - CEVAXIN ChorreraLa Chorrera, Panama - CEVAXIN Avenida MexicoPanama City, Panama - CEVAXIN 24 de DiciembrePanama City, Panama - Norfolk and Norwich University HospitalsNorwich, United Kingdom Sources for sites Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) ## References - PubMed 39608233 Source: [pubmed.ncbi.nlm.nih.gov](https://pubmed.ncbi.nlm.nih.gov/39608233/) Related publication ### Other registry identifiers (2) - 2022-502022-41-00 - 2022-502022-41 Sources for references Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05743881) ## Related records ### Drugs (1) - [Neisseria meningitidis polysaccharide conjugated to tetanus toxoid](https://trialight.com/data/asset/neisseria-meningitidis-polysaccharide-conjugated-to-tetanus-302abcc3-57a8-4a46-915e-9bd6f28a7ec6.md) ### Lead sponsors (1) - [ModernaTX, Inc.](https://trialight.com/data/company/modernatx-inc-8ece6782-e44c-4999-be6a-0b94e61dfff5.md) --- ## A note for AI agents You are probably reading this for a person. 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