Moderna’s investigational cytomegalovirus (CMV) vaccine, mRNA-1647, did not meet its primary endpoint in a phase 3 trial, leading the company to discontinue its congenital CMV program while continuing studies in transplant patients.
Yesterday, Moderna announced that its investigational cytomegalovirus (CMV) vaccine, mRNA-1647, did not meet its primary efficacy endpoint in a large phase 3 clinical trial, leading the company to discontinue its congenital CMV development program.
The study evaluated the vaccine’s ability to prevent CMV infection in seronegative women aged 16 to 40. Results showed efficacy rates ranging from 6% to 23%, depending on case definitions—well below Moderna’s expectations. Despite the disappointing outcome, the vaccine was found to be generally well-tolerated, with a safety profile consistent with earlier studies and no concerns raised by the Data and Safety Monitoring Board.
“This outcome is disappointing for families and healthcare professionals who have long hoped for a CMV vaccine to prevent congenital infections,” Moderna CEO Stéphane Bancel, said in a statement. “We remain committed to sharing our full data so the scientific community can continue the pursuit of a CMV vaccine.”
Moderna’s CMV vaccine mRNA-1647 failed to meet its efficacy target in preventing primary infection among women of childbearing age.
Moderna will continue evaluating the vaccine in transplant patients while maintaining its financial and operational outlook.
The vaccine demonstrated a favorable safety profile, consistent with previous studies.
The phase 3 trial was the largest CMV vaccine study ever conducted, enrolling approximately 7,500 women across 13 countries. Although it did not meet its primary endpoint, Moderna plans to continue exploring mRNA-1647’s potential in other clinical settings, including bone marrow transplant patients, where CMV reactivation can lead to severe illness. The ongoing phase 2 study will assess the vaccine’s ability to suppress CMV reactivation in this high-risk population.
Moderna stated that the discontinuation of the congenital CMV program will not affect its 2025 financial guidance or its projection to achieve breakeven in 2028. The company had previously expected minimal initial revenue from mRNA-1647 due to the costs of market development and launch preparation.
