Adults 6 Months to 11, any sex, with SARS-CoV-2. Patients with the condition only — healthy volunteers not accepted.
Results — posted to ClinicalTrials.gov
Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.
Parts 1, 2, and 3: Number of Participants With Solicited Local and Systemic Adverse Reactions (ARs)Primary· 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" s
Parts 1, 2, and 3: Number of Participants With Unsolicited AEsPrimary· 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 eve
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 StudyPrimary· 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 extern
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 P301Primary· 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 tim
Group
Value
95% CI
Part 1 (2-5 Years): mRNA-1273 25 µg
1012.5
848.2 – 1208.6
Part 1 (2-5 Years): mRNA-1273 50 µg
1845.9
1600.5 – 2128.9
Part 1 (6-23 Months): mRNA-1273 25 µg
1782.6
1542.0 – 2060.7
Part 1 (6-11 Years): mRNA-1273 50 µg
1669.1
1504.5 – 1851.6
Part 1 (6-11 Years): mRNA-1273 100 µg
1890.2
1603.8 – 2227.7
Part 2 (6-11 Years): mRNA-1273 50 µg
1618.3
1460.0 – 1793.9
Study mRNA-1273-P301 (NCT04470427) mRNA-1273 100 μg
1321.9
1196.5 – 1460.5
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 P301Primary· 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 rec
Group
Value
95% CI
Part 2 (2-5 Years): mRNA-1273 25 µg
1394.1
1267.7 – 1533.1
Part 2 (6-23 Months): mRNA-1273 25 µg
1759.8
1606.7 – 1927.4
Part 3 (6-11 Years): Primary Series mRNA-1273 25 µg
4368.6
3339.6 – 5714.6
Study mRNA-1273-P301 (NCT04470427) mRNA-1273 100 μg
1400.4
1272.7 – 1541.0
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 P301Primary· 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 SAR
Group
Value
95% CI
Part 1 (6-11 Years): mRNA-1273 50 µg
99.5
97.3 – 99.9
Part 1 (6-11 Years): mRNA-1273 100 µg
100
93.6 – 100.0
Part 1 (2-5 Years): mRNA-1273 25 µg
100
92.9 – 100
Part 1 (2-5 Years): mRNA-1273 50 µg
100
94.7 – 100.0
Part 1 (6-23 Months): mRNA-1273 25 µg
100
96.2 – 100.0
Part 2 (6-11 Years): mRNA-1273 50 µg
99.0
97.2 – 99.8
Study mRNA-1273-P301 (NCT04470427) mRNA-1273 100 μg
99.3
97.6 – 99.9
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 P301Primary· 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
Group
Value
95% CI
Part 2 (2-5 Years): mRNA-1273 25 µg
98.9
96.9 – 99.8
Part 2 (6-23 Months): mRNA-1273 25 µg
100
98.6 – 100.0
Part 3 (6-11 Years): Primary Series mRNA-1273 25 µg
88.5
77.8 – 95.3
Study mRNA-1273-P301 (NCT04470427) mRNA-1273 100 μg
99.3
97.6 – 99.9
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 P301Primary· 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 assess
Group
Value
95% CI
Study mRNA-1273-P301 (NCT04470427) mRNA-1273 100 μg
BD Part 1 and 2 (6-11 Yrs): PS mRNA-1273 50 μg - BD 1273 25 μg
5575.9
5026.8 – 6184.9
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 P301Primary· 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 crit
Group
Value
95% CI
Part 3 (6-11 Years): BD mRNA-1273 25 µg
4616.6
3669.4 – 5808.3
Study mRNA-1273-P301 (NCT04470427) mRNA-1273 100 μg
1400.4
1272.7 – 1541.0
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 P301Primary· 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, ha
Group
Value
95% CI
Study mRNA-1273-P301 (NCT04470427) mRNA-1273 100 μg
BD Part 1 and 2 (6-11 Yrs): PS mRNA-1273 50 μg - BD 1273 25 μg
100
97.2 – 100.0
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 P301Primary· 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, h
Group
Value
95% CI
Part 3 (6-11 Years): BD mRNA-1273 25 µg
90.0
78.2 – 96.7
Study mRNA-1273-P301 (NCT04470427) mRNA-1273 100 μg
99.3
97.6 – 99.9
Parts 1 and 2: GM Level of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2) S Protein-specific Binding Antibody (bAb), as Measured by MesoScale Discovery (MSD) Electrochemiluminescence (ECL) Multiplex Assay on Days 1 and 57Secondary· Day 1, Day 57 (1 month after Dose 2)
GM level of SARSCOV2S2P immunoglobulin G (IgG) antibody VAC123/VAC72, as measured by ECL multiplex assay specific to SARS-CoV-2 spike protein is reported. Antibody values reported as \<LLOQ were replaced by 0.5\*LLOQ and values \>ULOQ were replaced by ULOQ if actual values were not available. LLOQ was 23 AU/mL and ULOQ was 14000000 AU/mL for VAC72. LLOQ was 69 AU/mL and ULOQ was 14400000 AU/mL for VAC123. PP Immunogenicity Subset: all enrolled participants who received planned doses of study vaccine per schedule, had baseline SARS-CoV-2 status, had baseline and Day 57 antibody assessment, comp
Baseline (Day 1)
Group
Value
95% CI
Part 1 (6-11 Years): mRNA-1273 50 µg
35.6
31.0 – 40.8
Part 1 (6-11 Years): mRNA-1273 100 µg
49.1
33.9 – 71.1
Part 1 (2-5 Years): mRNA-1273 25 µg
15.8
13.5 – 18.5
Part 1 (2-5 Years): mRNA-1273 50 µg
33.7
26.2 – 43.4
Part 1 (6-23 Months): mRNA-1273 25 µg
14.6
12.8 – 16.7
Part 2 (6-11 Years): mRNA-1273 50 µg
32.6
28.5 – 37.3
Part 2 (2-5 Years): mRNA-1273 25 µg
24.5
21.7 – 27.5
Part 2 (6-23 Months): mRNA-1273 25 µg
22.0
19.1 – 25.3
Day 57
Group
Value
95% CI
Part 1 (6-11 Years): mRNA-1273 50 µg
325784.0
302917.7 – 350376.4
Part 1 (6-11 Years): mRNA-1273 100 µg
457349.2
402424.0 – 519770.8
Part 1 (2-5 Years): mRNA-1273 25 µg
261952.0
227935.8 – 301044.7
Part 1 (2-5 Years): mRNA-1273 50 µg
417419.8
359399.2 – 484807.0
Part 1 (6-23 Months): mRNA-1273 25 µg
297561.7
234740.9 – 377194.3
Part 2 (6-11 Years): mRNA-1273 50 µg
293118.9
261748.3 – 328249.4
Part 2 (2-5 Years): mRNA-1273 25 µg
235059.2
198610.2 – 278197.3
Part 2 (6-23 Months): mRNA-1273 25 µg
293955.4
256077.7 – 337435.8
Adverse events — posted to ClinicalTrials.gov
Time frame: Up to 2 years.
Reporting threshold: 5%.
Adverse-event reports describe events observed during the trial — not all are caused by the drug.
Part 1 (6-11 Years): mRNA-1273 50 µg
Serious: 5/380 (1%)
Deaths: 0/380
Part 1 (6-11 Years): mRNA-1273 100 µg
Serious: 3/371 (1%)
Deaths: 0/371
Part 1 (2-5 Years): mRNA-1273 25 µg
Serious: 0/69 (0%)
Deaths: 0/69
Part 1 (2-5 Years): mRNA-1273 50 µg
Serious: 0/155 (0%)
Deaths: 0/155
Part 1 (6-23 Months): mRNA-1273 25 µg
Serious: 3/150 (2%)
Deaths: 0/150
Part 2 (6-11 Years): Placebo
Serious: 1/995 (0%)
Deaths: 0/995
Part 2 (6-11 Years): mRNA-1273 50 µg
Serious: 22/3007 (1%)
Deaths: 0/3007
Part 2 (2-5 Years): Placebo
Serious: 3/1007 (0%)
Deaths: 0/1007
Part 2 (2-5 Years): mRNA-1273 25 µg
Serious: 32/3031 (1%)
Deaths: 0/3031
Part 2 (6-23 Months): Placebo
Serious: 7/666 (1%)
Deaths: 0/666
Part 2 (6-23 Months): mRNA-1273 25 µg
Serious: 45/1994 (2%)
Deaths: 0/1994
Part 3 (6-11 Years): Primary Series mRNA-1273 25 µg
Serious: 1/90 (1%)
Deaths: 0/90
Part 2(6-11 Yrs): PS PBO - mRNA-1273 50 μg (Crossover)
The primary goal for this study is to evaluate up to 3 dose levels of mRNA-1273 vaccine given to healthy children as intramuscular (IM) injection in 2 doses (in Parts 1 and 2) and 3 doses (in Part 3), and a third dose or an optional booster dose (BD) (in Parts 1 and 2).
Publications & conference data
8 peer-reviewed publications reference this trial (live from Europe PMC):
NCT07266558 — A Study to Evaluate the Efficacy and Safety of mRNA-1283 and mRNA-1273 in Participants 50 to 64 Years of Age Without Hig
· Phase 4
· recruiting
NCT06113692 — A Study on the Clinical Course, Outcomes and Risk Factors of Myocarditis and Pericarditis After Moderna COVID-19 Vaccine
· completed
NCT05345873 — A Study to Evaluate the Immunogenicity and Safety of a Recombinant Protein COVID-19 Vaccine as a Booster Dose in Populat
· Phase 2
· unknown
NCT05397223 — A Study of Modified mRNA Vaccines in Healthy Adults
· Phase 1
· completed
NCT05375838 — A Safety, Reactogenicity, and Immunogenicity Study of mRNA-1073 (COVID-19/Influenza) Vaccine in Adults 18 to 75 Years Ol
· Phase 1, PHASE2
· completed
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Publications: Europe PMC API search by NCT ID, retrieved 10 June 2026
Drug + disease cross-links: matched in real time against Drug Landscape's normalised drug + company + condition tables
Sponsor: as reported to ClinicalTrials.gov by ModernaTX, Inc.
Last refreshed: 13 June 2025
Drug Landscape aggregates and links these public records for informational use only. Always verify against the primary source before clinical or regulatory decisions. Canonical URL: https://druglandscape.com/trial/NCT04796896.