> Trialight public data. Index of pages: https://trialight.com/llms.txt > Web page: https://trialight.com/data/trial/a-study-to-evaluate-the-safety-and-immunogenicity-of-the-c5884a87-f118-48ed-a2d3-4f1544830774 > Record changed: 2026-10-13 # A Study to Evaluate the Safety and Immunogenicity of the mRNA COVID-19 Vaccines in Healthy Children Between 6 Months to Less Than 6 Years of Age NCT05436834 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) Phase Phase 3 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) Recruitment status Completed Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) Participants 1,807 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) Lead sponsor ModernaTX, Inc. Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) Start date 2022-06-21 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) Number of sites 74 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) ## Title and summary **Summary** This study will evaluate the safety and immunogenicity of the mRNA-1273.214 vaccine for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant of concerns (VOCs) in participants aged 6 months to \\<6 years, when administered as a primary series in SARS-CoV-2 vaccine-naïve participants (Part 1) and a single booster dose (BD) given to participants who previously received 2 doses of the mRNA-1273 vaccine as a primary series (Part 2); and will evaluate the safety and immunogenicity of the mRNA-1273.815 vaccine, when administered as a BD in participants aged 6 months to \\<6 years (Part 3) and when administered to SARS-CoV-2 vaccine-naïve participants aged 2 years to \\<5 years of age (Part 4). Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Short title** A Study to Evaluate the Safety and Immunogenicity of the mRNA COVID-19 Vaccines in Healthy Children Between 6 Months to Less Than 6 Years of Age Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Official title** An Open-Label, Phase 3 Study to Evaluate the Safety and Immunogenicity of mRNA Vaccines for SARS-CoV-2 Variants in Participants Aged 6 Months to < 6 Years Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) ## Status and phase **Control arm** Open label Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Registry reports results** No Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Listing at source** Listed Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Recruitment status** Completed Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Phase** Phase 3 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Study type** Interventional Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) ## Dates **Completion date** 2025-10-20 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **First posted** 2022-06-29 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Registry last updated** 2025-11-26 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Primary completion date** 2025-10-20 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Start date** 2022-06-21 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) ## Size and sites **Actual participants** 1,807 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Participants** 1,807 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Participant count basis** Actual Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Protocol amendments** 4 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Number of sites** 74 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) ## Sponsor and oversight **Registry sponsor category** Industry Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Lead sponsor** ModernaTX, Inc. Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Source registry** ClinicalTrials.gov Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) ## Identifiers **Registry ID** NCT05436834 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **ClinicalTrials.gov ID** NCT05436834 Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) **Registry record** Open registry record Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) ## Study design **Allocation** Not randomised **Model** Sequential **Purpose** Prevention **Masking** No masking Sources for study design Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) ## Outcomes ### Primary outcomes 1. Number of Participants with Solicited Local and Systemic Adverse Reactions (ARs) Timeframe: Up to Day 8 (7 days post-vaccination) 2. Number of Participants with Unsolicited Adverse Events (AEs) Timeframe: Up to Day 29 (28 days after each injection) 3. Number of Participants with Medically-Attended AEs (MAAEs) Timeframe: Up to Day 394 (12 months after last dose) 4. Number of Participants with Serious AEs (SAEs) Timeframe: Up to Day 394 (12 months after last dose) 5. Number of Participants with Adverse Events of Special Interest (AESI) Timeframe: Up to Day 394 (12 months after last dose) 6. Number of Participants with AEs Leading to Withdrawal Timeframe: Up to Day 394 (12 months after last dose) 7. Geometric Mean (GM) of the Serum Antibody (Ab) Level against Omicron BA.1 and Ancestral SARS-CoV-2 after mRNA-1273.214 Administration at Day 57 Timeframe: Day 57 8. GM of the Serum Ab Level against Omicron BA.1 and Ancestral SARS-CoV-2 after mRNA-1273.214 Administration at Day 29 Timeframe: Day 29 9. Seroresponse Rate (SRR) against Omicron BA.1 and Ancestral SARS-CoV-2 after mRNA-1273.214 Administration Timeframe: Day 29 10. GM of the Serum Ab Level against Omicron XBB.1.5 after mRNA-1273.815 Administration Timeframe: Up to Day 57 ### Secondary outcomes 1. SRR against Omicron BA.1 and Ancestral SARS-CoV-2 after mRNA-1273.214 Administration Regardless of prior SARS-CoV-2 Infection Timeframe: Day 57 2. GM of the Serum Ab Level against Omicron XBB.1.5 after mRNA-1273.815 Administration Regardless of prior SARS-CoV-2 Infection Timeframe: Up to Day 57 3. SRR against Omicron XBB.1.5 after mRNA-1273.815 Administration Regardless of prior SARS-CoV-2 Infection Timeframe: Up to Day 57 Sources for outcomes Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) ## Eligibility **Sex** All **Age groups** Children **Minimum age** 6 Months **Maximum age** 5 Years **Healthy volunteers** Yes ### Inclusion criteria - The participant is 6 months to <6 years for Parts 1, 2, and 3; 2 years to <5 years for Part 4A; and 6 months to <2 years for Part 4B at the time of consent (Screening Visit). Note: for Part 1, participant must be at least 6 months old and must not have reached 6 years of age at the time of administration of first dose. For Part 4B, the participant must be at least 6 months old and must not have reached 2 years of age at the time of administration of first dose. - If the participant has a chronic disease (that is, asthma, diabetes mellitus, cystic fibrosis, human immunodeficiency virus \[HIV\] infection), the disease should be stable, per investigator assessment, so that the participant can be considered eligible for inclusion. Stable diseases are those which have had no change in their status or in the medications required to control them in the 6 months prior to Screening Visit. Note: a change in medication for dose optimization (that is, insulin dose changes, adjustments for age-related weight gain), change within class of medication, or reduction in dose are not considered signs of instability. - In the investigator's opinion, the parent(s)/legally authorized representative(s) (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 2 years or older and has a body mass index (BMI) at or above the second percentile according to World Health Organization (WHO) Child Growth Standards at the Screening Visit. OR - The participant is less than 2 years of age and the participant's height and weight are both at or above the second percentile according to WHO Child Growth Standards at the Screening Visit. Special inclusion criteria for participants aged 6 months to < 12 months: - The participant was born at full-term (≥ 37 weeks gestation) with a minimum birth weight of 2.5 kilograms (kg). Inclusion criteria for Part 2: - The participant must have received 2 doses of mRNA-1273, approximately 28 to 35 days apart, as 25-μg primary series, and second dose was given at least 4 months prior to enrollment. Inclusion criteria for Part 3 only: \- The participant must have received an age-appropriate immunization series of an authorized/approved COVID-19 vaccine, with the last dose given at least 4 months prior to enrolment (Previous vaccines NOT allowed are: XBB.1.5-containing formulation). ### Exclusion criteria - Has a known history of SARS-CoV-2 infection (that is, reported AE of COVID-19 or asymptomatic SARS-CoV-2 infection during Study mRNA-1273-P204 at the time of rollover into mRNA-1273-P306 or during Part 1 at the time of rollover into Part 3) in the 90 days prior to dosing in this study. - Is acutely ill or febrile 24 hours prior to or at the Screening Visit. Fever is defined as a body temperature ≥ 38.0°Celsius (C)/≥ 100.4°Fahrenheit (F). Participants who meet this criterion may have visits rescheduled within the relevant study visit windows. Afebrile participants with minor illnesses can be enrolled at the discretion of the investigator. - For Parts 1 and 4, participant has previously been administered an investigational or approved CoV (that is, SARS-CoV-2, SARS-CoV, Middle East respiratory syndrome coronavirus \[MERS-CoV\]) vaccine. For Part 2, participant who received any approved/investigational CoV vaccine are ineligible to participate except for those who received mRNA-1273 (prototype) vaccine. - Has undergone treatment with investigational or approved agents for prophylaxis against COVID-19 (including receipt of SARS-CoV-2 monoclonal antibodies for prophylaxis or treatment) within 90 days prior to enrollment. - 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 COVID-19 vaccine or any of its components (including polyethylene glycol \[PEG\] or immediate allergic reaction of any severity to polysorbate). - Has a medical or psychiatric 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. - Has a history of diagnosis or condition that, in the judgment of the investigator, may affect study endpoint assessment or compromise participant safety, specifically the following: - Congenital or acquired immunodeficiency, other than well-controlled HIV infection. - Chronic hepatitis or suspected active hepatitis - A bleeding disorder that is considered a contraindication to IM injection or phlebotomy - Dermatologic conditions that could affect local solicited AR assessments - Any prior diagnosis of malignancy (excluding nonmelanoma skin cancer) - Has received the following: - Any routine vaccination with inactivated or live vaccine(s) within 14 days prior to study vaccination or plans to receive such a vaccine through 14 days following study vaccination. Note: This excludes influenza vaccine that may be given anytime, but ideally at least 7 days before study dose. If a participant receives an influenza vaccine, this should be captured within the concomitant medication electronic case report form (eCRF). - Systemic immunosuppressants or immune-modifying drugs for >14 days in total within 6 months prior to the day of enrollment (for corticosteroids, ≥1 milligrams (mg)/kg/day or ≥ 10 mg/day prednisone equivalent, if participant weighs >10 kg). Participants may have visits rescheduled for enrollment if they no longer meet this criterion within the Screening Visit window. Inhaled, nasal, and topical steroids, and palivizumab are allowed. - Intravenous (IV) or subcutaneous (SC) blood products (red cells, platelets, immunoglobulins) within 3 months prior to enrollment. Note: Other inclusion and exclusion criteria may apply. Sources for eligibility Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) ## Sites - Trinity Clinical Research, LLCBessemer, United States - Velcocity Clinical ResearchBanning, United States - Sera Collection Research ServicesMontebello, United States - Center For Clinical Trials LLC -ParamountParamount, United States - University of ColoradoAurora, United States - Meridian Clinical ResearchWashington D.C., United States - Prohealth Research CenterDoral, United States - University of Florida JacksonvilleJacksonville, United States - Kissimmee Clinical ResearchKissimmee, United States - Med-Care ResearchMiami, United States - University of South FloridaTampa, United States - IResearchDecatur, United States - Meridian Clinical ResearchMacon, United States - Velcocity Clinical ResearchMeridian, United States - Lurie Childrens HospitalChicago, United States - Meridian Clinical ResearchOverland Park, United States - Michael W. Simon MD, PSCLexington, United States - University of KentuckyLexington, United States - Velocity Clinical Research - Lafayette - PPDSLafayette, United States - MedPharmicsMetairie, United States - Velocity Clinical Research - Covington - PPDSMetairie, United States - Clinical Research InstituteMinneapolis, United States - University of Missouri Health CareColumbia, United States - Meridian Clinical ResearchHastings, United States - Meridian Clinical ResearchLincoln, United States And 49 more, listed on the interactive page. Sources for sites Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) ## References - PubMed 38518789 Source: [pubmed.ncbi.nlm.nih.gov](https://pubmed.ncbi.nlm.nih.gov/38518789/) Related publication Sources for references Source: [clinicaltrials.gov](https://clinicaltrials.gov/study/NCT05436834) ## Related records ### Drugs (1) - [Elasomeran](https://trialight.com/data/asset/elasomeran-7d917cbd-1f45-43e8-a188-fd6dec78e983.md) ### Lead sponsors (1) - [ModernaTX, Inc.](https://trialight.com/data/company/modernatx-inc-8ece6782-e44c-4999-be6a-0b94e61dfff5.md) ### Conditions (1) - [COVID-19](https://trialight.com/data/condition/covid-19-13f0ebf3-c291-557d-bdef-93563d077103.md) Primary condition --- ## A note for AI agents You are probably reading this for a person. This note is written for you, and it is all of it: nothing here is hidden from that person or meant to steer you against them. - Cite this page with its date. 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