A Study to Evaluate Safety and Effectiveness of mRNA-1273 COVID-19 Vaccine in Healthy Children Between 6 Months of Age and Less Than 12 Years of Age

Study at a glance

From the registry record, last updated by the sponsor on 13 Jun 2025. Recruitment status is as the sponsor reported it: confirm with the study team.

Official title

A Phase 2/3, Three-Part, Open-Label, Dose-Escalation, Age De-escalation and Randomized, Observer-Blind, Placebo-Controlled Expansion Study to Evaluate the Safety, Tolerability, Reactogenicity, and Effectiveness of mRNA-1273 SARS-CoV-2 Vaccine in Healthy Children 6 Months to Less Than 12 Years of Age

ClinicalTrials.gov ID

NCT04796896

Acronym / sponsor ID

mRNA-1273-P204

Conditions

SARS-CoV-2

Keywords

mRNA-1273, mRNA-1273 vaccine, SARS-CoV-2, SARS-CoV-2 Vaccine, Coronavirus, Virus Diseases, Messenger RNA, COVID-19

Phase

Phase 2/3

Study type

Interventional

Recruitment status

Completed

Enrolment

11,942 participants (actual)

Lead sponsor

ModernaTX, Inc.Industry (pharma, biotech, devices)

Study start

15 Mar 2021 (actual)

Primary completion

15 Mar 2024 (actual)

Study completion

15 Mar 2024 (actual)

First posted

15 Mar 2021 (actual)

Results

Posted 13 Jun 2025

Clinical summary

The research question as the sponsor registered it. This describes what the study plans to test, not what it found.

Study design

Primary purpose

Prevention

Allocation

Randomised

Intervention model

Parallel groups

Masking

Quadruple blind (participant, care provider, investigator, outcomes assessor)

Number of arms

2

Who may qualify

Ages

6 months to 11 years

Sex

All

Healthy volunteers

Accepted

Age groups

Child

Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.

Interventions

Primary outcome

1. Parts 1, 2, and 3: Number of Participants With Solicited Local and Systemic Adverse Reactions (ARs)

   Time frame: 7 days post-vaccination

   Solicited ARs were collected in an electronic diary (eDiary). Local ARs: injection site pain, erythema (redness), swelling/induration (hardness); and axillary (underarm) swelling or tenderness ipsilateral to the side of injection. Systemic ARs: fever, headache, fatigue, myalgia, arthralgia, nausea/vomiting, and chills. Note, not all solicited ARs were considered adverse events (AEs). Investigator reviewed whether the solicited AR was also to be recorded as an AE. A Summary of serious AEs (SAEs) and nonserious AEs ("Other"), regardless of causality, is located in the "Reported Adverse Events" section.

2. Parts 1, 2, and 3: Number of Participants With Unsolicited AEs

   Time frame: Up to 28 days post-vaccination

   An AE was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. Any abnormal laboratory test result (hematology, clinical chemistry, or prothrombin time [PT]/partial thromboplastin time [PTT]) or other safety assessment (for example, electrocardiogram, radiological scan, vital sign measurement), including one that worsened from baseline and was considered clinically significant in the medical and scientific judgment of the Investigator was recorded as an AE. COVID-19/SARS-CoV-2 infections were considered clinical events for efficacy and not AEs. A summary of SAEs and all nonserious AEs ("Other"), regardless of causality, is located in the "Reported Adverse Events" section and presented by each dose group separately.

3. Parts 1, 2, and 3: Number of Participants With Serious Adverse Events (SAEs), AEs of Special Interest (AESIs), Medically Attended AEs (MAAEs), and AEs Leading to Discontinuation From Study

   Time frame: Up to 2 years

   An SAE was defined as any AE that resulted in death, was life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in disability, was a congenital anomaly/birth defect, or was an important medical event. AESIs for mRNA-1273 were identified based upon medical concepts that may be related to COVID-19 or were of interest in COVID-19 vaccine safety surveillance. An MAAE is an AE that led to an unscheduled visit to a healthcare practitioner. This included visits to a study site for unscheduled assessments and visits to healthcare practitioners external to the study site. COVID-19/SARS-CoV-2 infections were considered clinical events for efficacy and not AEs. A summary of SAEs and all nonserious AEs ("Other"), regardless of causality, is located in the "Reported Adverse Events" section and presented by each dose group separately.

4. Parts 1 and 2: Geometric Mean (GM) Value of Serum Pseudovirus Neutralizing Antibody ID50 Titers From Study mRNA-1273-P204 (P204) Vaccine Recipients at Day 57 Compared With Those From Young Adult (18 to 25 Years) Vaccine Recipients (Day 57) in Study P301

   Time frame: Day 57 P204/Day 57 P301

   Antibody values reported as below lower limit of quantification (LLOQ) were replaced by 0.5*LLOQ and values greater than upper limit of quantification (ULOQ) were replaced by ULOQ if actual values were not available. LLOQ was 18.5 arbitrary units (AU)/milliliter (mL) and ULOQ was 45118 AU/mL for ID50 titer. Per-Protocol (PP) Immunogenicity Subset: all enrolled participants who received planned doses of the study vaccine per schedule, had baseline SARS-CoV-2 status, had baseline and Day 57 antibody assessment for analysis endpoint, complied with immunogenicity window based on 2nd injection timing; had negative reverse transcriptase polymerase chain reaction (RT-PCR) test for SARS-CoV-2 and negative serology test based on binding antibody (bAb) specific to SARS-CoV-2 nucleocapsid protein at baseline, not receiving highly active antiretroviral therapy (HAART) for participants with HIV; and had no major protocol deviations that impacted key or critical data.

5. Parts 2 and 3: GM Concentration of Serum Pseudovirus Neutralizing Antibody VAC62 From Study P204 Vaccine Recipients at Day 57 Compared With Those From Young Adult (18 to 25 Years of Age) Vaccine Recipients (Day 57) in Study P301

   Time frame: Day 57 P204/Day 57 P301

   Antibody values reported as below LLOQ were replaced by 0.5*LLOQ and values >ULOQ were replaced by ULOQ if actual values were not available. LLOQ was 10 AU/mL and ULOQ was 111433 AU/mL. PP Immunogenicity Subset: all enrolled participants who received planned doses of the study vaccine per schedule, had baseline SARS-CoV-2 status, had baseline and Day 57 antibody assessment, complied with immunogenicity window based on 2nd injection timing; had negative RT-PCR test for SARS-CoV-2 and negative serology test based on bAb specific to SARS-CoV-2 nucleocapsid protein at baseline in Part 2, not receiving HAART in participants with HIV; and had no major protocol deviations that impacted key/critical data. Since the number of participants enrolled in Part 3 was substantially smaller than the planned sample size required for immunogenicity hypothesis testing after Dose 2 of mRNA-1273 25 μg primary series and after a 3rd dose of mRNA-1273 25 μg, the hypothesis testing was not performed.

6. Parts 1 and 2: Seroresponse Rate (SRR) For Serum Pseudovirus Neutralizing Antibody ID50 From Study P204 Vaccine Recipients at Day 57 Compared With Those From Young Adult (18 to 25 Years of Age) Vaccine Recipients (Day 57) in Study P301

   Time frame: Day 57 P204/Day 57 P301

   Percentage of participants with seroresponse for pseudovirus neutralizing antibody ID50 are reported. Seroresponse: change from below LLOQ to equal above 4*LLOQ, or at least a 4-fold rise if baseline is ≥LLOQ. LLOQ=18.5 AU/mL and ULOQ=45118 AU/mL for ID50 titer. PP Immunogenicity Subset: all enrolled participants who received planned doses of study vaccine, had baseline SARS-CoV-2 status, had baseline and Day 57 antibody assessment, complied with immunogenicity window based on 2nd injection timing; had negative RT-PCR test for SARS-CoV-2 and negative serology test based on bAb specific to SARS-CoV-2 at baseline, not receiving HAART; and had no major protocol deviations that impacted key/critical data. Since the number of participants enrolled in Part 3 was substantially smaller than the planned sample size required for immunogenicity hypothesis testing after Dose 2 of mRNA-1273 25 μg primary series and after a 3rd dose of mRNA-1273 25 μg, the hypothesis testing was not performed.

7. Parts 2 and 3: SRR For Serum Pseudovirus Neutralizing Antibody VAC62 From Study P204 Vaccine Recipients at Day 57 Compared With Those From Young Adult (18 to 25 Years of Age) Vaccine Recipients (Day 57) in Study P301

   Time frame: Day 57 P204/Day 57 P301

   Percentage of participants with seroresponse for Pseudovirus Neutralizing Antibody VAC62 are reported. Seroresponse was defined as a change from below the LLOQ to equal above 4 * LLOQ, or at least a 4-fold rise if baseline is equal to or above the LLOQ. LLOQ was 10 and ULOQ AU/mL was 111433 AU/mL. PP Immunogenicity Subset: all enrolled participants who received planned doses of the study vaccine per schedule, had baseline SARS-CoV-2 status, had baseline and Day 57 antibody assessment for analysis endpoint, complied with immunogenicity window based on 2nd injection timing; had negative RT-PCR test for SARS-CoV-2 and negative serology test based on bAb specific to SARS-CoV-2 nucleocapsid protein at baseline in Part 2, not receiving HAART in participants with HIV; and had no major protocol deviations that impacted key or critical data.

8. Parts 1 and 2: GM Concentration of Post-booster Dose Serum Pseudovirus Neutralizing Antibody VAC62 in Study P204 Compared With Post-primary Series (Post-Dose 2) in Young Adult (18 to 25 Years of Age) Vaccine Recipients in Study P301

   Time frame: BD-Day 29 P204/Day 57 P301

   Antibody values reported as below the LLOQ were replaced by 0.5*LLOQ and values greater than the ULOQ were replaced by ULOQ if actual values were not available. LLOQ was 10 AU/mL and ULOQ was 111433 AU/mL. PP Immunogenicity Subset (Booster Dose Analysis): all enrolled participants who received 2 doses of planned doses of mRNA-1273 vaccination in Part 1 open-label phase or Part 2 blinded phase per schedule, received booster dose in Booster Dose Analysis, not receiving HAART in participants with HIV, had a negative SARS-CoV-2 status at baseline (pre-dose 1 of mRNA-1273), had BD-Day 29 Ab assessment for the analysis endpoint, no major protocol deviations that impacted key or critical data, and had not received off-study COVID-19 vaccination prior to BD-Day 29 visit.

9. Part 3: GM Concentration of Post-third Dose Serum Pseudovirus Neutralizing Antibody VAC62 in Study P204 Compared With Post-primary Series (Post-Dose 2) in Young Adult (18 to 25 Years) Vaccine Recipients in Study P301

   Time frame: Third Dose-Day 29 P204/Day 57 P301

   Antibody values reported as below the LLOQ were replaced by 0.5*LLOQ and values greater than the ULOQ were replaced by ULOQ if actual values were not available. LLOQ was 10 AU/mL and ULOQ was 111433 AU/mL. PP Immunogenicity Subset (Third Dose Analysis): all enrolled participants who received first 2 doses of planned doses of mRNA-1273 vaccination in Part 3 open-label phase per schedule, received third dose in Third Dose Analysis, not receiving HAART in participants with HIV, had BD-Day 29 antibody assessment for the analysis endpoint, had no major protocol deviations that impacted key or critical data, and had not received off-study COVID-19 vaccination prior to BD-Day 29 visit. Since the number of participants enrolled in Part 3 was substantially smaller than the planned sample size required for immunogenicity hypothesis testing after Dose 2 of mRNA-1273 25 μg primary series and after a 3rd dose of mRNA-1273 25 μg, the hypothesis testing was not performed.

10. Parts 1 and 2: SRR for Post-booster Dose Serum Pseudovirus Neutralizing Antibody VAC62 From Baseline (Pre-Dose 1) Compared With Post-primary Series (Post-Dose 2) From Baseline (Pre-Dose 1) in Young Adult (18 to 25 Years) Vaccine Recipients in Study P301

    Time frame: BD-Day 29 P204/Day 57 P301

    Percentage of participants with seroresponse for Pseudovirus Neutralizing Antibody VAC62 are reported. Seroresponse was defined as a change from below the LLOQ to equal above 4 * LLOQ, or at least a 4-fold rise if baseline is equal to or above the LLOQ. LLOQ was 10 AU/mL and ULOQ was 111433 AU/mL. PP Immunogenicity Subset (Booster Dose Analysis): all enrolled participants who received 2 doses of planned doses of mRNA-1273 vaccination in Part 1 open-label phase or Part 2 blinded phase per schedule, received booster dose in Booster Dose Analysis, not receiving HAART in participants with HIV, had a negative SARS-CoV-2 status at baseline (pre-dose 1 of mRNA-1273), had BD-Day 29 Ab assessment for the analysis endpoint, no major protocol deviations that impacted key or critical data, and had not received off-study COVID-19 vaccination prior to BD-Day 29 visit.

11. Part 3: SRR for Post-third Dose Serum Pseudovirus Neutralizing Antibody VAC62 From Baseline (Pre-Dose 1) Compared With Post-primary Series (Post-Dose 2) From Baseline (Pre-Dose 1) in Young Adult (18 to 25 Years) Vaccine Recipients in Study P301

    Time frame: Third Dose-Day 29 P204/Day 57 P301

    Percentage of participants with seroresponse for Pseudovirus Neutralizing Antibody VAC62 are reported. Seroresponse was defined as a change from below the LLOQ to equal above 4 * LLOQ, or at least a 4-fold rise if baseline is equal to or above the LLOQ. LLOQ was 10 AU/mL and ULOQ was 111433 AU/mL. PP Immunogenicity Subset (Third Dose Analysis): all enrolled participants who received first 2 doses of planned doses of mRNA-1273 vaccination in Part 3 open-label phase per schedule, received third dose in Third Dose Analysis, not receiving HAART in participants with HIV were not receiving HAART, had BD-Day 29 antibody assessment for the analysis endpoint, had no major protocol deviations that impacted key or critical data, and had not received off-study COVID-19 vaccination prior to BD-Day 29 visit.

Results and safety

Loading the posted results from ClinicalTrials.gov…

Research links

• Official record on ClinicalTrials.govLast updated by the sponsor 13 Jun 2025.
• Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
• Derived from this study: PubMed 40119775Rostad CA, Campbell JD, Paulsen GC, Ghamloush SS, Xu W, Zheng L, McElrath MJ, De Rosa SC, Girard B, Das R, Anderson EJ, Creech CB. Evaluation of Cellular Immune Responses After mRNA-1273 Vaccination in Children 6 Months to 11 Years of Age. J Infect Dis. 2025 Jun 2;231(5):e945-e955. doi: 10.1093/infdis/jiaf144.
• Derived from this study: PubMed 39158584Berthaud V, Creech CB, Rostad CA, Carr Q, de Leon L, Dietrich M, Gupta A, Javita D, Nachman S, Pinninti S, Rathore M, Rodriguez CA, Luzuriaga K, Towner W, Yeakey A, Brown M, Zhao X, Deng W, Xu W, Zhou H, Girard B, Kelly R, Slobod K, Anderson EJ, Das R, Miller J, Schnyder Ghamloush S. Safety and Immunogenicity of an mRNA-1273 Booster in Children. Clin Infect Dis. 2024 Dec 17;79(6):1524-1532. doi: 10.1093/cid/ciae420.
• Derived from this study: PubMed 38518789Dixit A, Bennett R, Ali K, Griffin C, Clifford RA, Turner M, Poston R, Hautzinger K, Yeakey A, Girard B, Zhou W, Deng W, Zhou H, Schnyder Ghamloush S, Kuter BJ, Slobod K, Miller JM, Priddy F, Das R; ROVER Study Investigators. Interim safety and immunogenicity of COVID-19 omicron BA.1 variant-containing vaccine in children in the USA: an open-label non-randomised phase 3 trial. Lancet Infect Dis. 2024 Jul;24(7):687-697. doi: 10.1016/S1473-3099(24)00101-4. Epub 2024 Mar 19.
• Derived from this study: PubMed 36260859Anderson EJ, Creech CB, Berthaud V, Piramzadian A, Johnson KA, Zervos M, Garner F, Griffin C, Palanpurwala K, Turner M, Gerber J, Bennett RL, Ali K, Ampajwala M, Berman G, Nayak J, Chronis C, Rizzardi B, Muller WJ, Smith CA, Fuchs G, Hsia D, Tomassini JE, DeLucia D, Reuter C, Kuter B, Zhao X, Deng W, Zhou H, Ramirez Schrempp D, Hautzinger K, Girard B, Slobod K, McPhee R, Pajon R, Aunins A, Das R, Miller JM, Schnyder Ghamloush S; KidCOVE Study Group. Evaluation of mRNA-1273 Vaccine in Children 6 Months to 5 Years of Age. N Engl J Med. 2022 Nov 3;387(18):1673-1687. doi: 10.1056/NEJMoa2209367. Epub 2022 Oct 19.
• Derived from this study: PubMed 35544369Creech CB, Anderson E, Berthaud V, Yildirim I, Atz AM, Melendez Baez I, Finkelstein D, Pickrell P, Kirstein J, Yut C, Blair R, Clifford RA, Dunn M, Campbell JD, Montefiori DC, Tomassini JE, Zhao X, Deng W, Zhou H, Ramirez Schrempp D, Hautzinger K, Girard B, Slobod K, McPhee R, Pajon R, Das R, Miller JM, Schnyder Ghamloush S; KidCOVE Study Group. Evaluation of mRNA-1273 Covid-19 Vaccine in Children 6 to 11 Years of Age. N Engl J Med. 2022 May 26;386(21):2011-2023. doi: 10.1056/NEJMoa2203315. Epub 2022 May 11.
• Derived from this study: PubMed 34870630Lynch LR, Clifford H, Ko R, Hache M, Sun W. Primer of COVID-19 Vaccines for the Perioperative Physician. J Neurosurg Anesthesiol. 2022 Jan 1;34(1):101-106. doi: 10.1097/ANA.0000000000000802.
• Click here to access the website, http://www.kidcovestudy.com, for additional information for the study, such as Study Overview, Participation, Site Locations, along with contact numbers for each location for the study.Link provided by the sponsor.

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Referral and contact

AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.

The record lists no contact. Use the official record to reach the sponsor.

91 sites in 2 countries: see every site and its status.