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# Moderna Quits CMV Vaccine After Phase 3 Failure
- URL: https://www.fdaweb.com/moderna-quits-cmv-vaccine-after-phase-3-failure/
- Published: 2025-10-22T12:00:00.000Z
- Updated: 2026-09-14T15:24:43.000Z
- Author: David McFarland
- Tags: Biologics, #legacy-id-D5160089

Moderna’s bid to bring the first vaccine for congenital cytomegalovirus (CMV) to market has ended in disappointment. The company says its investigational CMV vaccine, mRNA-1647, failed to meet the primary endpoint in a large Phase 3 trial, prompting the company to discontinue development for use in preventing congenital CMV. The vaccine showed efficacy ranging from just 6% to 23%, well below Moderna’s target for preventing primary CMV infection, it says. CMV, a common herpesvirus, is typically harmless in healthy adults but can cause severe birth defects when passed from a pregnant person to a fetus.

While Moderna is ending its congenital CMV program, the company says it will continue testing mRNA-1647 in a Phase 2 trial in bone marrow transplant patients, where CMV reactivation can cause serious illness.