Moderna vaccine shows promise for teens in large trial

NCT ID NCT04649151

Vaccine Sponsor: ModernaTX, Inc. Source: ClinicalTrials.gov ↗

First seen Jun 26, 2026 · Last updated Jun 26, 2026

Summary

This completed Moderna trial tested the mRNA-1273 COVID-19 vaccine in over 4,300 healthy adolescents aged 12 to 17. The study looked at safety, side effects, and how well the vaccine works to prevent COVID-19. Participants received either the vaccine or a placebo, and some later got a booster dose targeting the Omicron variant.

What this could mean

Our plain-language read of the trial. This is informational only, not medical advice or a prediction.

Active substance: mRNA-1273 (COVID-19 vaccine)
What this could lead to: If successful, this could show that the Moderna COVID-19 vaccine is safe and effective for adolescents, helping protect them from COVID-19.
What could go wrong: This trial is completed, but results may not apply to newer variants or other populations. Side effects like injection site pain and fever were monitored.

This is an AI summary of the original study and may miss details. Read our disclaimer.

Study facts

What this study's own registry entry says, in plain language.

Phase

Phase 2/3

Runs two stages together: whether the treatment works, then large-scale confirmation.

Participants

4,328 people

The number who actually took part.

Started

Dec 2020

Finished

Jun 2024

Lead sponsor

A company

The lead sponsor is a pharmaceutical, biotech, or medical-device company.

Who can take part

This study's own entry requirements. Only the study team can say for certain whether you qualify.

Ages

12 to 18 years

Sex

Anyone

Healthy volunteers

Accepted

You do not need to have the condition being studied to take part.

Show the full entry requirements

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: For Part 1A, Part 2 and Part 3: * Participants 12 to \<18 years of age at the time of consent (Screening Visit, Day 0) who, in the opinion of the Investigator, are in good general health based on review of medical history and screening physical examination. * Investigator assessment that the participant, in the case of an emancipated minor, or parent(s)/legally acceptable representative(s) (LAR\[s\]) understand and is willing and physically able to comply with protocol-mandated follow up, including all procedures and provides written informed consent/assent. * Body mass index (BMI) at or above the third percentile according to World Health Organization (WHO) Child Growth Standards at the Screening Visit (Day 0) * Female participants of nonchildbearing potential may be enrolled in the study. Nonchildbearing potential is defined as premenarche or surgically sterile (history of bilateral tubal ligation, bilateral oophorectomy, hysterectomy). * Female participants of childbearing potential may be enrolled in the study if the participant has a negative pregnancy test at Screening (Day 0), on the day of the first injection (Day 1), on the day of the second injection (Day 29 in Parts 1A and Part 2, and Day 181 in Part 3); has practiced adequate contraception or has abstained from all activities that could result in pregnancy for at least 28 days prior to the first injection (Day 1); and has agreed to continue adequate contraception or abstinence through 3 months following the second injection (Day 29 in Part 1A and Part 2, and Day 181 in Part 3). For Part 1B: * Participants must have been previously enrolled in mRNA-1273-P203 study. * Female participants of childbearing potential may be enrolled in the study if the participant has a negative pregnancy test on the day of the first injection (Open-Label-Day 1) and on the day of the second injection (Open-Label-Day 29). For Part 1C-1 Homologous Booster Dose: * Participants must have been previously enrolled in the mRNA-1273-P203 study, are actively participating in Part 1A or Part 1B and are least 5 months from the last dose. * Female participants of childbearing potential may be enrolled in the study if the participant has a negative pregnancy test on the day of the first injection (BD-Day 1). Part 1C-2 Heterologous Booster Dose: * Male or female, 12 to \< 18 years of age at the time of consent who, in the opinion of the investigator, is in good general health based on review of medical history and screening physical examination AND has completed non-Moderna primary COVID-19 vaccination series under EUA (for example, Pfizer) at least 3 months from consent. Exclusion Criteria: For Part 1A, Part 2, and Part 3: * Has a known history of SARS-CoV-2 infection within 2 weeks prior to administration of investigational product (IP) or known close contact with anyone with laboratory-confirmed SARS-CoV-2 infection of COVID-19 within 2 weeks prior to administration of IP (Part 2 participants only). For Part 3 participants, known history of SARS-CoV-2 infection within 90 days prior to administration of IP or known close contact with anyone with laboratory-confirmed SARS-CoV-2 infection or COVID-19 within 90 days prior to administration of IP. * Travel outside of the United States or home country (Part 2 and Part 3 only) in the 28 days prior to the Screening Visit (Day 0). * Pregnant or breastfeeding * Is acutely ill or febrile 24 hours prior to or at the Screening Visit (Day 0). Fever is defined as a body temperature ≥38.0°Celsius (C)/≥100.4°Farenheit (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. * Prior administration of an investigational coronavirus (for example, SARS-CoV-2, SARS-CoV, Middle East Respiratory Syndrome \[MERS-CoV\]) vaccine * Current treatment with investigational agents for prophylaxis against COVID-19 * Has a medical, psychiatric, or occupational condition that may pose additional risk as a result of participation, or that could interfere with safety assessments or interpretation of results according to the Investigator's judgment * Current use of any inhaled substance (for example, tobacco or cannabis smoke, nicotine vapors) * History of chronic smoking (≥1 cigarette a day) within 1 year of the Screening Visit (Day 0) * History of illegal substance use or alcohol abuse within the past 2 years. This exclusion does not apply to historical cannabis use that was formerly illegal in the participant's state but is legal at the time of screening. * History of a diagnosis or condition that, in the judgment of the Investigator, may affect study endpoint assessment or compromise participant safety, specifically: * Congenital or acquired immunodeficiency, including human immunodeficiency virus (HIV) infection * Suspected active hepatitis * Has a bleeding disorder that is considered a contraindication to IM injection or phlebotomy * Dermatologic conditions that could affect local solicited AR assessments * History of anaphylaxis, urticaria, or other significant AR requiring medical intervention after receipt of a vaccine * Diagnosis of malignancy within the previous 10 years (excluding nonmelanoma skin cancer) * Febrile seizures * Receipt of: * Any licensed vaccine within 28 days before the first dose of IP or plans for receipt of any licensed vaccine within 28 days before and/or after each dose of IP. * Systemic immunosuppressants or immune-modifying drugs for \>14 days in total within 6 months prior to the day of enrollment (for corticosteroids, ≥20 mg/day prednisone equivalent). Topical tacrolimus is allowed if not used within 14 days prior to the day of enrollment. Participants may have visits rescheduled for enrollment if they no longer meet this criterion within the Screening Visit window. Inhaled, nasal, and topical steroids are allowed. * Intravenous blood products (red cells, platelets, immunoglobulins) within 3 months prior to enrollment * Has donated ≥450 milliliters (mL) of blood products within 28 days prior to the Screening Visit (Day 0) or plans to donate blood products during the study * Participated in an interventional clinical study within 28 days prior to the Screening Visit (Day 0) or plans to do so while participating in this study * Is an immediate family member or has a household contact who is an employee of the research center or otherwise involved with the conduct of the study For Part 1C-1 and Part 1C-2: * Pregnant or breastfeeding. * Is acutely ill or febrile 24 hours prior to or at the Screening Visit (Day 0). Fever is defined as a body temperature ≥ 38.0°C/≥ 100.4°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. * Has a medical, psychiatric, or occupational condition that may pose additional risk as a result of participation, or that could interfere with safety assessments or interpretation of results according to the investigator's judgment. * History of a diagnosis or condition (after enrolment in Part 1A) that, in the judgment of the investigator, may affect study endpoint assessment or compromise participant safety: * Suspected active hepatitis * Has a bleeding disorder that is considered a contraindication to IM injection or phlebotomy * Dermatologic conditions that could affect local solicited AR assessments * History of anaphylaxis, urticaria, or other significant AR requiring medical intervention after receipt of a vaccine * Diagnosis of malignancy (excluding nonmelanoma skin cancer) * Receipt of: • Any authorized or licensed vaccine within 28 days before the first dose of IP or plans for receipt of any licensed vaccine through 28 days following the last dose of IP or any seasonal influenza vaccine within 14 days before the first dose of IP or plans for receipt of any seasonal influenza vaccine 14 days following the last dose of IP. * Participated in an interventional clinical study, other than mRNA-1273-P203 study, within 28 days prior to the Screening Visit (Day 0 \[for Part 1C-1\], BD-Day 0 \[for Part 1C-2\]) or plans to do so while participating in this study. Part 1C-2 Heterologous Booster Dose: * Has a known history of SARS-CoV-2 infection within 2 weeks prior to administration of IP or known close contact with anyone with laboratory-confirmed SARS-CoV-2 infection or COVID 19 within 2 weeks prior to administration of IP.

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Conditions

The condition(s) this trial relates to.

Coronavinae infectious disease viral infectious disease COVID-19 prevention target

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

SARS-CoV-2

Contacts and locations

Locations

ACRC Trials

Frisco, Texas, 75033, United States
Accel Research Sites - Nona Pediatric Center - ERN - PPDS

Orlando, Florida, 32829, United States
Advanced Clinical Research - Jordan Valley - ERN - PPDS

West Jordan, Utah, 84088, United States
Alliance for Multispecialty Research

Syracuse, Utah, 84075, United States
Alliance for Multispecialty Research -El Dorado

El Dorado, Kansas, 67042, United States
Altus Research - Hunt - PPDS

Lake Worth, Florida, 33461, United States
Benchmark Research

Austin, Texas, 78705, United States
Caimed Dominicana S.A.S

Santo Domingo, Nacional, Dominican Republic
Child Healthcare Associates - East Syracuse

East Syracuse, New York, 13210, United States
Clinical Research Atlanta

Stockbridge, Georgia, 30281, United States
Clinical Research Institute, Inc - CRN - PPDS

Minneapolis, Minnesota, 55402, United States
Clinical Trials of Texas, Inc. - PPDS

San Antonio, Texas, 78229, United States
Coastal Bend Research Center

Corpus Christi, Texas, 78404, United States
Coastal Carolina Research Center

North Charleston, South Carolina, 29405, United States
Coastal Pediatric Associates

Charleston, South Carolina, 29414, United States
Cope Family Medicine - Ogden Clinic - CCT

Bountiful, Utah, 84010, United States
Cottonwood Pediatrics

Murray, Utah, 84107, United States
Cyn3rgy Research - ClinEdge - PPDS

Gresham, Oregon, 97030, United States
DM Clinical Research - Kool Kids Pediatrics - ERN - PPDS

Houston, Texas, 77064, United States
Hospital General Regional Dr. Marcelino Velez Santana

Santo Domingo, Nacional, Dominican Republic
Hospital Materno Infantil San Lorenzo de Los Mina

Santo Domingo, Nacional, Dominican Republic
IACT Health - Roswell - IACT - HyperCore - PPDS

Columbus, Georgia, 31904, United States
Instituto Dermatologico y Cirugia de la Piel Dr. H Sede San Cristóbal

Santo Domingo, Nacional, Dominican Republic
Instituto Dominicano de Estudios Virologicos IDEV

Santo Domingo, Nacional, Dominican Republic
Johnson County Clin-Trials

Lenexa, Kansas, 66219, United States
Lynn Health Science Institute

Oklahoma City, Oklahoma, 73112, United States
Meridian Clinical Research (Endwell-New York) - Platinum - PPDS

Endwell, New York, 13901, United States
Meridian Clinical Research (Hastings-Nebraska) - Platinum - PPDS

Hastings, Nebraska, 68901, United States
Meridian Clinical Research (Norfolk, Virginia)

Norfolk, Virginia, 68701, United States
Meridian Clinical Research (Omaha-Nebraska) - Platinum - PPDS

Omaha, Nebraska, 68134, United States
Meridian Clinical Research (Sioux City - Iowa)

Sioux City, Iowa, 51106, United States
Meridian Clinical Research - (Macon Georgia) - Platinum - PPDS

Macon, Georgia, 31210, United States
Meridian Clinical Research - Charleston, SC

Charleston, South Carolina, 29414, United States
Meridian Clinical Research - Family Practice Ports - Portsmouth - Platinum - PPDS

Portsmouth, Virginia, 23703, United States
Olivo Medical and Wellness Center

Chicago, Illinois, 60618, United States
Paradigm Clinical Research

La Mesa, California, 91942, United States
Quality Clinical Research - HyperCore - PPDS

Omaha, Nebraska, 68114, United States
South Ogden Family Medicine/Ogden Clinic - CCT Research

South Ogden, Utah, 84405, United States
Sundance Clinical Research - Platinum - PPDS

St Louis, Missouri, 63141, United States
Tekton Research

San Antonio, Texas, 78229, United States
Tekton Research

San Antonio, Texas, 78244, United States
Tekton Research - Georgia - PPDS

Chamblee, Georgia, 30341, United States
University of Massachusetts Medical School, Molecu

Worcester, Massachusetts, 01655, United States
Velocity Clinical Research - Albuquerque - PPDS

Albuquerque, New Mexico, 87102, United States
Velocity Clinical Research - Banning

Banning, California, 92220, United States
Velocity Clinical Research - Boise - PPDS

Meridian, Idaho, 83642, United States
Velocity Clinical Research - Cincinnati - PPDS

Cincinnati, Ohio, 45242, United States
Velocity Clinical Research - Gulfport - PPDS

Gulfport, Mississippi, 39503, United States
Velocity Clinical Research - Metairie - PPDS

Metairie, Louisiana, 70006, United States
Velocity Clinical Research - Providence - PPDS

East Greenwich, Rhode Island, 02818, United States
Velocity Clinical Research - Valparaiso

Valparaiso, Indiana, 46383, United States
Vital Prospects Clinical Research Institute PC - CRN - PPDS

Tulsa, Oklahoma, 74136, United States
Wee Care Pediatrics - Kaysville

Kaysville, Utah, 84037, United States

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