A Phase 2 interventional study of mRNA-1647 and mRNA-1647 in Cytomegalovirus Infection, sponsored by ModernaTX, Inc.. Completed at 7 sites in United States. Open to participants aged 18 Years to 40 Years. Per ClinicalTrials.gov, last updated 2026-02-02.
Sponsored by ModernaTX, Inc. · Phase 2, Interventional, and Prevention
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.
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.
359 studies on the registry are indexed under Cytomegalovirus Infections; 59 are open to participants now.
This study's enrollment of 135 is above the median of 60 across 233 interventional studies indexed under Cytomegalovirus Infections.
Browse Cytomegalovirus Infections studies →ModernaTX, Inc. is the lead sponsor of 112 studies on the registry; 14 are open to participants now.
Of its 60 completed or terminated interventional studies of FDA-regulated products, 32 (53%) have results posted.
Counted across the registry records on this site, refreshed daily.
Primary Extension Phase:
Optional Booster Phase:
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.
Exclusion Criteria:
Primary Extension Phase:
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.
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
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.
Biological: mRNA-1647
Participants who opted to enroll into the optional Booster Phase will receive a single mRNA-1647 vaccine dose.
Other: mRNA-1647
Participants who opted to enroll into the Observational Group will be followed in the optional BP until BP Month 12.
Biological: mRNA-1647
No investigational product will be administered during the Primary Extension Phase or to the participants in the Observational Group.
Lyophilized product that is reconstituted with saline then diluted with a special diluent to reach the desired concentration
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
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
This study is completed, as verified in Jan 2026. You cannot join it, but the record below documents what was studied.
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ModernaTX, Inc.