Cytomegalovirus InfectionPhase 2NCT04975893
A Long-Term Extension Study to Evaluate the Immunogenicity and Safety of Cytomegalovirus (CMV) mRNA-1647 Vaccine
A Phase 2 study testing mRNA-1647 in people with Cytomegalovirus Infection, run by ModernaTX, Inc. at 7 sites in United States.
Trial summary
The main purpose of the extension phase of this study is to evaluate the longer-term immune persistence of mRNA-1647 vaccine administered to CMV-seronegative and CMV-seropositive adults who completed Study mRNA-1647-P202 (NCT04232280). Read more about this study
- Who is it for?
- Ages 18 to 40 years
- Conditions the study is for
- Cytomegalovirus Infection
- What is being tested?
- mRNA-1647
- Type of treatment
- Vaccines
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 135 participants
- Where
- 7 sitesUnited States
- Study dates
- 18 Jun 2021to 19 Jan 2026
- Phase
- Phase 2
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 40 years
- All sexes
- No healthy volunteers
- Adult
Who may be able to join
- Primary Extension Phase:
- Male and female participants who were CMV-seronegative at the Study mRNA-1647-P202 Screening visit, completed the final Study mRNA-1647-P202 visit, and remained CMV-seronegative at Screening for Study mRNA-1647-P202-EXT.
- Male and female participants who were CMV-seropositive at the Study mRNA-1647-P202 Screening visit, were randomized to receive mRNA-1647 injection (and not placebo), and completed the final visit in Study mRNA-1647-P202.
- Understands and agrees to comply with the trial procedures and provides written informed consent.
- According to the assessment of the Investigator, is in good general health and is capable of complying with trial procedures.
- Optional Booster Phase:
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- For BD Recipients:
- CMV-seronegative and CMV-seropositive participants who received mRNA-1647 medium dose injection (and not placebo or other dose levels) in Study mRNA-1647-P202, including participants who enrolled in the Primary Extension Phase of Study mRNA-1647-P202-EXT and participants who were eligible but did not previously enroll in the Primary Extension Phase of Study mRNA-1647-P202-EXT are eligible to receive a BD in the optional BP.
- For Observational Group:
- CMV-seronegative and CMV-seropositive participants who received mRNA-1647 low dose or high dose injection (and not placebo or mRNA-1647 medium dose injection) in Study mRNA-1647-P202, including participants who enrolled in the Primary Extension Phase of Study mRNA-1647-P202-EXT and participants who were eligible but did not previously enroll in the Primary Extension Phase of Study mRNA-1647-P202-EXT are eligible to enroll in the observational group.
Who cannot join
- Primary Extension Phase:
- Receipt of any CMV vaccine other than mRNA-1647.
- Diagnosis or condition that, in the judgment of the Investigator, may affect participant safety, assessment of safety endpoints, assessment of immune response, or adherence to trial procedures, including any medical, psychiatric, or occupational condition that, in the opinion of the Investigator, might pose additional risk due to participation in the study or could interfere with the interpretation of study results.
- Optional Booster Phase:
- For BD Recipients:
- Participants from the placebo, mRNA-1647 low dose, or mRNA-1647 medium dose groups in Study mRNA-1647-P202.
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- For Observational Group:
- Participants from the placebo or mRNA-1647 medium dose groups in study mRNA-1647-P202.
- Note: Other protocol-defined inclusion/exclusion criteria apply
Trial locations and contacts
7 sites in 1 country.
7 sites in 1 country
United States7 sites
Tekton Research Inc
Austin, Texas, 78745
Johnson County Clin-Trials, Inc.
Lenexa, Kansas, 66219
Alliance for Multispeciality Research, LLC
Lexington, Kentucky, 40509
Optimal Research, LLC
Peoria, Illinois, 61610
J. Lewis Research, Inc. / Foothill Family Clinic South
Salt Lake City, Utah, 84109
J. Lewis Research, Inc. / Foothill Family Clinic South
Salt Lake City, Utah, 84121
Crossroads Clinical Research (Victoria)
Victoria, Texas, 77901
About this study
Official title: A Phase 2, Non-Randomized, Long-Term Extension Study to Evaluate the Immunogenicity and Safety of Cytomegalovirus mRNA-1647 Vaccine Including a Booster Dose in a Subset of Participants Who Completed Study mRNA-1647-P202
The main purpose of the extension phase of this study is to evaluate the longer-term immune persistence of mRNA-1647 vaccine administered to CMV-seronegative and CMV-seropositive adults who completed Study mRNA-1647-P202 (NCT04232280). For participants in the optional booster phase (BP), the main purpose is to evaluate the long-term immunogenicity and safety of the mRNA-1647 vaccine in both participants receiving a booster dose (BD) and those not receiving a BD, and to additionally evaluate the reactogenicity in participants receiving a BD.
Read the detailed description
The study aims to explore the long-term potential differences in immunogenicity and key safety parameters following mRNA-1647 administration, participants who completed study mRNA-1647-P202, who are CMV-seronegative and who did not seroconvert due to primary CMV infection during the study will be enrolled. Study mRNA-1647-P202 participants who were CMV-seropositive at baseline, randomized to receive mRNA-1647 injection, and completed their final study visit will also be enrolled.
No study treatment will be administered during the primary extension phase of this study. Eligible participants enrolling in the primary extension phase who completed Study mRNA-1647-P202 may have received mRNA-1647 (either low dose, medium dose, or high dose) or placebo in CMV-seronegative participants and mRNA-1647 (either low dose, medium dose, or high dose) in CMV-seropositive participants.
In the optional BP, consenting and eligible participants will receive a single BD of the mRNA-1647 vaccine (medium dose). In the Observational Group of the optional BP, consenting and eligible participants will not receive study treatment.
- Conditions
- Cytomegalovirus Infection
- Being tested
- mRNA-1647
- Keywords
- Moderna, mRNA-1647, Cytomegalovirus, CMV, Cytomegalovirus Vaccine, Cytomegalovirus Infections, Cytomegalovirus Congenital, Virus Diseases, Infection Viral, DNA Virus Infections, Messenger RNA
- Medical subject headings
- Cytomegalovirus Infections, Virus Diseases, DNA Virus Infections
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
mRNA-1647Biological
No investigational product will be administered during the Primary Extension Phase or to the participants in the Observational Group.
mRNA-1647Other
Lyophilized product that is reconstituted with saline then diluted with a special diluent to reach the desired concentration
| Study group | Role | What they receive |
|---|---|---|
| Primary Extension Phase | Other | CMV-seropositive and CMV-seronegative participants who completed Study mRNA-1647-P202 will be followed every 6 months for 3 years in this study after the final visit in Study mRNA-1647-P202. Receives: Biological: mRNA-1647 |
| Optional Booster Phase - BD Recipients | Experimental | Participants who opted to enroll into the optional Booster Phase will receive a single mRNA-1647 vaccine dose. Receives: Other: mRNA-1647 |
| Optional Booster Phase - Observational Group | Other | Participants who opted to enroll into the Observational Group will be followed in the optional BP until BP Month 12. Receives: Biological: mRNA-1647 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Primary Extension Phase: Geometric Mean Titers (GMTs) of Antigen-Specific Neutralizing Antibody (nAb) and Binding Antibody (bAb)
Measured: Up to 3 years
BP: GMTs of Antigen-Specific nAb and bAb
Measured: BP Month 0, BP Month 1, BP Month 3, BP Month 6, and BP Month 12
BP: Number of Participants with Solicited Adverse Reactions (ARs)
Measured: Up to BP Day 7 (7 days after BP vaccination)
BP: Number of Participants with Unsolicited Adverse Events (AEs)
Measured: Up to BP Day 28 (28 days after BP vaccination)
BP: Number of Participants with Medically-Attended AEs (MAAEs)
Measured: Up to BP Month 6 (6 months after BP vaccination)
BP: Number of Participants with Adverse Events of Special Interest (AESIs), Serious Adverse Events (SAEs), and AEs Leading to Discontinuation of Study
Measured: Up to BP Month 12
Secondary outcomes (2)
Primary Extension Phase: Number of Participants With AEs Leading to Study Discontinuation
Measured: Up to 3 years
Primary Extension Phase: Number of Participants With SAEs
Measured: Up to 3 years
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted26 Jul 2021
- Study start18 Jun 2021
- Primary completion19 Jan 2026
- Study completion19 Jan 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Cytomegalovirus InfectionStudies of the same condition, open and under way.
- More trials run by ModernaTX, Inc.The sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2
- Primary purpose
- Prevention
- Allocation
- Non-randomised
- Intervention model
- Sequential
- Masking
- None (open label)
- Enrolment
- 135 participants (actual)
Sponsor and investigators
- Lead sponsor
- ModernaTX, Inc.
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04975893
- Sponsor's protocol ID
- mRNA-1647-P202-EXT
- Status last verified
- Jan 2026
- First submitted
- 9 Jul 2021
- Last updated
- 2 Feb 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 2 Feb 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Phase 2, Non-Randomized, Long-Term Extension Study to Evaluate the Immunogenicity and Safety of Cytomegalovirus mRNA-1647 Vaccine Including a Booster Dose in a Subset of Participants Who Completed Study mRNA-1647-P202
- ClinicalTrials.gov ID
- NCT04975893
- Acronym / sponsor ID
- mRNA-1647-P202-EXT
- Conditions
- Cytomegalovirus Infection
- Keywords
- Moderna, mRNA-1647, Cytomegalovirus, CMV, Cytomegalovirus Vaccine, Cytomegalovirus Infections, Cytomegalovirus Congenital, Virus Diseases
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 135 participants (actual)
- Lead sponsor
- ModernaTX, Inc.Industry (pharma, biotech, devices)
- Study start
- 18 Jun 2021 (actual)
- Primary completion
- 19 Jan 2026 (actual)
- Study completion
- 19 Jan 2026 (actual)
- First posted
- 26 Jul 2021 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The main purpose of the extension phase of this study is to evaluate the longer-term immune persistence of mRNA-1647 vaccine administered to CMV-seronegative and CMV-seropositive adults who completed Study mRNA-1647-P202 (NCT04232280). For participants in the optional booster phase (BP), the main purpose is to evaluate the long-term immunogenicity and safety of the mRNA-1647 vaccine in both participants receiving a booster dose (BD) and those not receiving a BD, and to additionally evaluate the reactogenicity in participants receiving a BD.
Detailed description
The study aims to explore the long-term potential differences in immunogenicity and key safety parameters following mRNA-1647 administration, participants who completed study mRNA-1647-P202, who are CMV-seronegative and who did not seroconvert due to primary CMV infection during the study will be enrolled. Study mRNA-1647-P202 participants who were CMV-seropositive at baseline, randomized to receive mRNA-1647 injection, and completed their final study visit will also be enrolled.
No study treatment will be administered during the primary extension phase of this study. Eligible participants enrolling in the primary extension phase who completed Study mRNA-1647-P202 may have received mRNA-1647 (either low dose, medium dose, or high dose) or placebo in CMV-seronegative participants and mRNA-1647 (either low dose, medium dose, or high dose) in CMV-seropositive participants.
In the optional BP, consenting and eligible participants will receive a single BD of the mRNA-1647 vaccine (medium dose). In the Observational Group of the optional BP, consenting and eligible participants will not receive study treatment.
Study design
- Primary purpose
- Prevention
- Allocation
- Non-randomised
- Intervention model
- Sequential
- Masking
- None (open label)
- Number of arms
- 3
| Arm | Type | Receives |
|---|---|---|
| Primary Extension Phase | Other | Biological: mRNA-1647CMV-seropositive and CMV-seronegative participants who completed Study mRNA-1647-P202 will be followed every 6 months for 3 years in this study after the final visit in Study mRNA-1647-P202. |
| Optional Booster Phase - BD Recipients | Experimental | Other: mRNA-1647Participants who opted to enroll into the optional Booster Phase will receive a single mRNA-1647 vaccine dose. |
| Optional Booster Phase - Observational Group | Other | Biological: mRNA-1647Participants who opted to enroll into the Observational Group will be followed in the optional BP until BP Month 12. |
Who may qualify
- Ages
- 18 to 40 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult
Key inclusion criteria (10 listed)
- Male and female participants who were CMV-seronegative at the Study mRNA-1647-P202 Screening visit, completed the final Study mRNA-1647-P202 visit, and remained CMV-seronegative at Screening for Study mRNA-1647-P202-EXT.
- Male and female participants who were CMV-seropositive at the Study mRNA-1647-P202 Screening visit, were randomized to receive mRNA-1647 injection (and not placebo), and completed the final visit in Study mRNA-1647-P202.
- Understands and agrees to comply with the trial procedures and provides written informed consent.
- According to the assessment of the Investigator, is in good general health and is capable of complying with trial procedures.
- CMV-seronegative and CMV-seropositive participants who received mRNA-1647 medium dose injection (and not placebo or other dose levels) in Study mRNA-1647-P202, including participants who enrolled in the Primary Extension Phase of Study mRNA-1647-P202-EXT and participants who were eligible but did not previously enroll in the Primary Extension Phase of Study mRNA-1647-P202-EXT are eligible to receive a BD in the optional BP.
Key exclusion criteria (9 listed)
- Receipt of any CMV vaccine other than mRNA-1647.
- Diagnosis or condition that, in the judgment of the Investigator, may affect participant safety, assessment of safety endpoints, assessment of immune response, or adherence to trial procedures, including any medical, psychiatric, or occupational condition that, in the opinion of the Investigator, might pose additional risk due to participation in the study or could interfere with the interpretation of study results.
- Participants from the placebo, mRNA-1647 low dose, or mRNA-1647 medium dose groups in Study mRNA-1647-P202.
- Participants from the placebo or mRNA-1647 medium dose groups in study mRNA-1647-P202.
- Note: Other protocol-defined inclusion/exclusion criteria apply
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| mRNA-1647No investigational product will be administered during the Primary Extension Phase or to the participants in the Observational Group. | Biological | Optional Booster Phase - Observational Group, Primary Extension Phase |
| mRNA-1647Lyophilized product that is reconstituted with saline then diluted with a special diluent to reach the desired concentration | Other | Optional Booster Phase - BD Recipients |
Primary outcome
Primary Extension Phase: Geometric Mean Titers (GMTs) of Antigen-Specific Neutralizing Antibody (nAb) and Binding Antibody (bAb)
Time frame: Up to 3 years
BP: GMTs of Antigen-Specific nAb and bAb
Time frame: BP Month 0, BP Month 1, BP Month 3, BP Month 6, and BP Month 12
BP: Number of Participants with Solicited Adverse Reactions (ARs)
Time frame: Up to BP Day 7 (7 days after BP vaccination)
BP: Number of Participants with Unsolicited Adverse Events (AEs)
Time frame: Up to BP Day 28 (28 days after BP vaccination)
BP: Number of Participants with Medically-Attended AEs (MAAEs)
Time frame: Up to BP Month 6 (6 months after BP vaccination)
BP: Number of Participants with Adverse Events of Special Interest (AESIs), Serious Adverse Events (SAEs), and AEs Leading to Discontinuation of Study
Time frame: Up to BP Month 12
2 secondary outcomes
Primary Extension Phase: Number of Participants With AEs Leading to Study Discontinuation
Time frame: Up to 3 years
Primary Extension Phase: Number of Participants With SAEs
Time frame: Up to 3 years
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 2 Feb 2026.
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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.
7 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing mRNA-1647 in people with Cytomegalovirus Infection, run by ModernaTX, Inc. at 7 sites in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 10 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 2 Feb 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 7 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Primary Extension Phase: Geometric Mean Titers (GMTs) of Antigen-Specific Neutralizing Antibody (nAb) and Binding Antibody (bAb) (time frame: Up to 3 years). The study lists 6 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 2 Feb 2026.