05:44 AM EDT, 10/23/2025 (MT Newswires) -- Moderna ( MRNA ) said Thursday that a phase 3 trial of mRNA-1647 investigational vaccine failed to meet its primary efficacy endpoint of preventing cytomegalovirus infection in seronegative women of childbearing age between 16 to 40 years.

The company said it will discontinue development of the investigational vaccine for congenital cytomegalovirus but continue the ongoing phase 2 trial to evaluate mRNA-1647 in bone marrow transplant patients.

Moderna ( MRNA ) said the vaccine was generally well tolerated and no safety concerns were identified.

Shares of Moderna ( MRNA ) fell 3.8% in recent Thursday premarket activity.