mRNA-1273 variant-containing COVID-19 vaccine: immune response and safety

A Phase 3b/4, Open-label Study to Assess the Immunogenicity and Safety of mRNA COVID-19 Variant-containing Vaccine Formulations

Phase 4 Interventional ModernaTX, Inc. · NCT06585241

This will test variant-containing mRNA-1273 COVID-19 vaccine formulations to see if they boost immunity and are safe for previously vaccinated adults and selected children with risk factors.

Quick facts

PhasePhase 4
Study typeInterventional
Enrollment1144 (estimated)
Ages6 Months and up
SexAll
SponsorModernaTX, Inc. Industry-sponsored
Locations6 sites (Atlanta, Georgia and 5 other locations)
Trial IDNCT06585241 on ClinicalTrials.gov

What this trial studies

This master-protocol uses a flexible design to test multiple updated mRNA-1273 formulations matched to circulating SARS-CoV-2 variants. Each formulation and age group is evaluated in a subprotocol with the same core procedures for vaccination, blood sampling for antibody and cellular immune responses, and safety monitoring. Participants are generally previously vaccinated individuals across adult and selected pediatric age groups. Not all endpoints apply to every subprotocol, allowing rapid evaluation as new variants emerge.

Who should consider this trial

Good fit: Ideal candidates are people who have already received prior COVID-19 vaccination and meet the specific subprotocol age and risk-factor criteria (for example adults ≥18 years, older adults ≥65, or children with at least one risk factor).

Not a fit: People who are unvaccinated, have contraindications to mRNA vaccines, or are severely immunocompromised with expected poor vaccine responses may not receive meaningful benefit.

Why it matters

Potential benefit: If successful, these variant-containing boosters could provide stronger and broader protection against circulating and newly emerged SARS-CoV-2 variants.

How similar studies have performed: Other mRNA booster programs, including bivalent and variant-targeted boosters, have increased neutralizing antibody levels and improved protection against Omicron subvariants.

Eligibility criteria

Show full inclusion / exclusion criteria
Key Inclusion Criteria:

* mRNA-1273.167 and mRNA-1273.712: Previously vaccinated adults aged ≥18 years
* mRNA-1273.251: Participants ≥65 years of age, ≥12 to \<65 years of age, or ≥6 months to \<12 years of age with at least 1 risk factor for severe outcomes from COVID-19.
* mRNA-1273.261: ≥65 years of age at the time of signing the informed consent or ≥18 to \<65 years of age at the time of signing the informed consent with at least 1 risk factor for severe outcomes from COVID-19.
* Able to comply with study procedures based on the assessment of the Investigator.
* Female participants of childbearing potential may be enrolled in the study if the participant fulfills all the following criteria:

  * Has a negative pregnancy test at the Screening Visit and on the day of vaccination prior to vaccine dose being administered on Day 1.
  * Has practiced adequate contraception or has abstained from all activities that could result in pregnancy for at least 28 days prior to the first dose.
  * Has agreed to continue adequate contraception through 28 days following vaccine administration.

Key Exclusion Criteria:

* History of SARS-CoV-2 infection within 3 months prior to enrollment for mRNA-1273.167 and mRNA-1273.712 or within up to 6 months prior to enrollment for mRNA-1273.251 and mRNA-1273.261.
* Is acutely ill or febrile (temperature 38.0°Celsius/100.4°Fahrenheit) less than 72 hours prior to or at the Screening Visit or Day 1. Participants meeting this criterion may be rescheduled within the Screening window.
* History of a diagnosis or condition that, in the judgment of the Investigator, is clinically unstable, or may affect participant safety, assessment of study endpoints, assessment of immune response, or adherence to study procedures.
* History of anaphylaxis or severe hypersensitivity reaction requiring medical intervention after receipt of any mRNA vaccine or therapeutic or any components of an mRNA vaccine or therapeutic.
* Receipt of COVID-19 vaccine within 3 months prior to enrollment for mRNA-1273.167 and mRNA-1273.712 or within 6 months prior to enrollment for mRNA-1273.251 and mRNA-1273.261.
* Receipt of any licensed non-COVID-19 vaccine within 14 days (inactivated vaccine, pediatric) or 28 days before or planned receipt within 14 days (pediatric) or 28 days after the study intervention, except an influenza vaccine, which may be given at least 7 days before (pediatric) or 14 days before or after receipt of the study intervention.
* Receipt of systemic immunosuppressants or immune-modifying drugs for \>14 days total (within 6 months prior to Screening for mRNA-1273.167 and mRNA-1273.712 or within 180 days prior to Screening for mRNA-1273.251 and mRNA-1273.261) or is anticipating the need for immunosuppressive treatment at any time during participation in the study.
* Receipt of systemic immunoglobulins, long-acting biological therapies that affect immune (pediatric) responses, or blood products (within 3 months prior to Screening for mRNA-1273.167 and mRNA-1273.712 or within 90 days prior to the Screening for mRNA-1273.251 and mRNA-1273.261) or plans for receipt during the study.
* Has donated ≥450 milliliters of blood products within 28 days prior to the Screening Visit or plans to donate blood products during the study.

Other protocol-defined inclusion/exclusion criteria may apply.

Where this trial is running

Atlanta, Georgia and 5 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions SARS-CoV-2mRNA-1273mRNA-1273 vaccineSARS-CoV-2 VaccineCoronavirusVirus DiseasesMessenger RNACOVID-19
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.