Moderna Stops CMV Vaccine After Phase III Failure

Moderna will discontinue development of its experimental CMV vaccine mRNA-1647 after the Phase III CMVictory trial of about 7,500 seronegative women aged 16–40 failed to meet its primary endpoint, showing efficacy roughly 6%–23%. The company said the candidate was generally well tolerated, that it will release additional trial data, and that a Phase II study in bone-marrow transplant patients will continue with results expected by August 2026. Executives expressed disappointment and noted the failure leaves the field without an approved congenital CMV vaccine despite decades of research. Moderna's shares fell several percent in after‑hours/premarket trading, but the company said the miss is not expected to change its 2025 guidance and that the product would have required substantial market-building investment and been initially cash-flow negative.